No speed limit on German highways - why?

The main reason may simply be that there doesn't need to be a speed limit, and that there never was a compelling reason to implement one. For the most part, freeway speeds are self-regulating.

Secondly, it is simply not true that there is no speed limit on the freeway. There is no general speed limit, but most stretches of the Autobahn do have individual speed limits. Only a few long-distance stretches between cities truly don't have a speed limit.

Those stretches are usually two lanes in each direction, and frequently heavily congested (during summer vacation traveling season, traffic jams of 100km are not unheard of). In winter, snow and ice also naturally limits speeds.

Basically, there are very few stretches and times when you really can drive very fast, often only in the middle of the night.

Keep in mind that in the USA, for a long time, there was no speed limit on the freeways, either. If it hadn't been for the 1970s oil crisis, there still would be no speed limit.

Disclaimer: things may have changed. It has been a quarter century since I lived in Germany.

Let me answer as a German with an analogy.

You can compare the German speed limit to weapon ownership in US. Any party suggesting introduction of a general speed limit would conduct political suicide and face serious debates with the automobile lobby and voters (most workplaces here come from this branch). Most rational arguments points towards a speed limit (less traffic jam/noise, environmental pollution...), but similar to US weapon industry, there are to many automobile fanatics in all political parties (either green, liberal, democrats, conservative). You can only lose voters with this topic.

The historical circumstances are simply that a lot of automobile inventions were made in Germany, the car is a status symbol for many here.

These articles sheds some light on the special situation in Germany:

When the introduction of a national speed limit for Germany's Autobahns (motorways and highways) was discussed in the 1980s, automobile associations of all kinds demanded the "Freedom of the roads for free citizens" – with at least some success back then. And even today, Germany still does not have a general speed limit. Although a maximum speed of 130 km/h is recommended, where no road sign expressly indicates this speed limit, drivers can decide for themselves how fast they would like to travel. If you should pick up a few angry comments about "Points in Flensburg" during a conversation, you can be sure that those involved are talking about the Kraftfahrt-Bundesamt (Federal Motor Transport Authority). Some 7.1 million car drivers are currently listed there. All of them ignored the signs and were caught driving too fast. The quicker they were travelling, the higher the fine and the number of points they collected. Travelling in your own car

Germany is seen as a country of car enthusiasts. No wonder then that this is where the first motor vehicle was invented. Today, the automotive industry is one of the country's largest employers. There is practically no other item that Germans would spend as much money on as a car. For students, having their own car is generally a luxury. The prices for petrol and diesel are higher than in other European countries and the required third-party insurance (Haftpflichtversicherung) also costs a lot of money. And still, many afford themselves the luxury of a car of their own.

Further:

The German "Economic Miracle" of the Fifties and Sixties were boom times for the car and road building industry. It was not until the world oil crisis of the early Seventies that the country's politicians were forced to contemplate the idea of speed restrictions on Autobhans. The then West German government reacted by imposing a ban on Sunday driving and introducing a 100kph speed limit for the duration of the crisis.

During the 111 days that the speed limit was in force, Germany's equivalent of Britain's Automobile Association, the 16-million member ADAC, got wind of government plans to make the restriction permanent. The immensely powerful organisation responded by promoting a slogan which has now become part of everyday German vocabulary: "Freie Fahrt Für Frei Bürger", which translates prosaically into (Limit) Free Driving for Free Citizens.

The massive public opposition to Autobahn speed limits that ensued had, until yesterday, stopped the idea from ever being taken up again by either of Germany's two main parties. Safety has hardly been an issue either, in fact the government has mounted campaigns stressing how statistically safe the Autobahn is in comparison to two-lane highways.

The German car lobby, headed by the influential giants, Mercedes, Volkswagen, Porsche and BMW, has for decades persuaded the political establishment to reject the idea of blanket motorway speed limits. To ensure the co-operation of the main parties, Daimler, BMW and Porsche donated a total of 2m (£1.4m) to them in the run up to Germany's 2005 general election.