What's the use of trains that spend 6+ hours of daytime en route?

Additional reasons:

• You may travel only a part of the route, so that the train arrives with mostly different passengers than it departed with.
• There may be more stops along the route, which people from smaller towns will use, as opposed to bullet train where you save 2H on the ride but then lose them over the last miles.
• Then again, if there is no direct flight between your destinations, you will often waste more time on taking the (long) connection.

I live in New Zealand.
I mainly travel by train only when “overseas”.
Overday train travel is by far my preference for train travelling.

I position myself at a suitable window – or even better a glass free opening if possible, array a camera or few and start taking photos.

India “hard sleeper” – 20 hours Chennai to Pune – OK – some of the trip was unavoidably at night.
2000+ photos – fields, crops, temples, houses, people, animals, much more ….

Qingdao – Beijing: Hundreds of photos of Chinese landscape, factories, villages, towns, … .

Marvellous!

Last train out of Rome – you can’t win them all :-).

I have traveled to over 100 European cities and I find traveling in overday time, always refreshing. These are my advantages when traveling about 5-6 hours in daytime.

Hotel check-in at 2 PM

Most hotels have check-in time at 1400 and checkout time at 1200. So I start early morning by train 8 AM (or even earlier) and will correctly reach in time to check in (I don’t have to wait in hotels to check-in)

Beautiful countryside views

You can enjoy most beautiful countryside views only in broad day light.

Safety

I felt so much safer traveling in broad daylight in a new country, new place, new people, rather than at night. I have heard that so many burglaries happen at night in buses or trains when people are asleep.

Passport control

When crossing borders by train or bus, at nights, passport checks are done and officers usually bang at door, wake you up in the middle of night. This essentially kills your sleep.

Friendly pals

You have chance to meet nice friends in trains or bus and have nice conversation with people nearby in day time, during travel. Certainly not at night.

Stranded

If you happen to miss your late night train or bus, you are stranded. This is not a problem when traveling at daytime. You will have several alternatives.

In addition to what has been said so far:

Some people might not feel secure sleeping in a train. They might be scared of someone climbing in at a stop and going out with their bag immediately or at the next stop (even though night trains typically have less stops than daytime trains). During daytime you would notice if anyone took your bag. Same for suitcases, many people put their suitcases at a place where they can see it even if it is 10 or 20 meters away.

It can also be imagined that harassment is more frequent or unnoticed at night than during daytime.

I personally like overnight trains, but I can easily imagine that many people feel that way.

Also, a senior citizen might probably prefer the accessibility of a real bed, and might not mind wasting a day even if they don’t enjoy train travel.

In the UK we have “cross country” trains, these often take most of a day to get from one end to the other. However most passengers only spend a few hours on the trains, as they get on and off at intermediate stops.
It is common to find a faster train if you do wish to go “end to end”, that is a direct intercity.

Before I will consider flying a train will have to take at least 4 hours more than the plane, due to time to get to/from the airport, check in time, luggage processing time, risk of problems and the airports not being very nice taking my drinks from me etc. I also get more legroom on the train, and don’t have to sit in an airport for 1hr or so on a uncomfortable seat.

Just not having the risk of a £50 fine, if I don’t pre-book enough checkin luggage, or wasted money if I book too much makes the train a lot lower stress option. The last flight I took, I got prodded in the back many times by the person behind me, I have never had this happen on a train.

You can enjoy the view

Tourists who are visiting a country for the first time may enjoy watching the city/country go by. My husband and I enjoy often choose to take the train while travelling for this reason. It’s an easy, cheap, relaxing way to view the country you’re visiting, especially the chance to gain a snapshot of locals going on with their lives in the countryside.

You can be productive

There is freedom of movement on a train and access to useful facilities: wifi, food, bathroom access, and cellphone reception. One may do some work, or read, or spend time with family. Trains are a much less stressful mode of travel for families with small kids, and this becomes a chance to play games and have family time while on holiday. I often used to play chess with my family while we travelled by train.

You pay less

Overnight trips are more expensive. It’s cheaper to book a seat than a bunk. Seats use less space, so more can be fit onto a train.

Overnight is not always an option

Many routes only run during the day. It’s more expensive for a company to pay people to work overnight. Locals will be using the trains during the day, but only long distance travellers will at night. If the train makes several stops along the way, then stopping at night becomes impractical.

Overnight is not always comfortable (Thanks @Zach Lipton)

Some people find it difficult to sleep in an unfamiliar bed or on a train bunk (or worse, in a seat!). It may not offer the quality of sleep one is used to. Especially if a person is easily awoken and disturbed by the movement of the train.

For some, it’s not time wasted

To a person who is only concerned with the destination, overnight travel would seem more practical than daytime travel, but for many tourists or other people who choose to use the train, it’s as much about enjoying the journey as it is about the destination.

You are not the only one of the train.
While you go the six hour distance, most long distance trains have people getting on and off at all stations it stops.
With day time trains that is well possible, with overnight trains those stops will fall at odd times of the night.

And your six hour journey may well be part of a much longer train travel, with the train arriving two days later in its final stop. In that case the total travel will be part day and part overnight.

In some places you have options, in others you take what you can get.
For Europe, most of the long distance trains do run by day, only very few run overnight and very rarely a train runs for more than 24 hours. And those get more rare still.
In Australia, Canada and the USA you find fewer trains per day on the lines but more often they do run for much longer stretches, going for more than one night and often just one train departure each 24 hours or even per 48 hours.
In those areas you mostly do not have choice, there are often just day trains or just night trains, with some rare occasions where there are both day and night trains. There you take the train you can get or go with an other kind of transport instead.

Personal preferences and plans for the next day do matter.
I love train travel and will often take a train instead of a flight to go to far away places and see something of the area you pass through.
When they were still available I did sometimes take the night train to Paris so I could arrive at my final destination in France in daylight. On the way home I was always happy to spend all day on the train so I got home that same day.
Night travel is not comfortable, often requiers booking far in advance and is often more expensive.
Most people do prefer to sleep in their own beds over sleeping in a night train to arrive home early in the morning.
Getting a bed in the train is not too bad, sitting up in a chair the day before you have to do work or sight seeing is not everybodies choice.

In places the options disappeared, with you left with just day trains.
In Europe with the coming of the fast trains overnight trains are disappearing. And I can understand why. The overnight train from Amsterdam to Copenhagen left at 19:00, so 7 PM, to arrive at 11:30 the next day.
For tourists on the move that would mean that they would need to catch the train after an early dinner, there not being a full dinner service on the train, and still lose most of the day in Copenhagen on arrival.
The stops in Germany would all be in the night, so almost no travelers for Germany would take the train, there being day trains as well.

A good site.
For more information on train travel, almost everywhere in the world, you can have a look at the Site of the Man in Seat Sixty-One.
He has many long distance routes, showing options by night train where available and often having much shorter travel times for the day connections between the same cities.

Depending on where you come from and where you want to go, flying could be much less practical. Many train stations are in the city centres, airports are outside. So the choice may be this:

• One hour to the airport, one hour or more checking in, hassle with security checks, boarding, then one or two hours of flight, collect the baggage, another hour to the destination.
• Half an hour to the train station, arrive with just a few minutes to spare, several hours of train ride, then half an hour to the destination.

If there is no direct connection and you have to switch planes/trains, the aircraft look even worse. I’d probably choose the trains even if the total is one or two hours longer, simply to avoid the aggravation of the airport. I can read a good book in a train seat, but not in a line in the airport.

Tourism? I LOVE travelling by train, and do so when I have time available – you get to see so much during the day!

Also, we can’t run all trains at night, some schedules connect with others, or you have more people who can only travel during the day (shift work), some don’t like sleeping on a train at night – many, many reasons.

Also, if a train takes 6 hours to get somewhere, if it goes back immediately, you can get 3-4 runs in during a 24 hour period. If you have to run them all at night, firstly, you reduce the available services, and secondly, might sell out that service every time, while you could have been getting money during the day as well.

Also some countries require you pay more for night workers, and unions have various rules about night time work, councils have noise laws about trains running through certain areas at night, and so on.

Long story short – there are many good reasons, and you should really try a long day time trip – it’s fun!