Why didn't God omit non-essential information from the Bible?

Short answer: Just because it's not important to us doesn't mean it's not important to someone.

There's the phrase that you might hear from time to time: "One man's trash is another man's treasure". Though our culture finds those details irrelevant, not all cultures do. Since the Bible is written to all cultures, these details must exist in order to be effective in those places.

For example, some remaining tribal cultures, such as some of those in Papua New Guinea. For some tribal cultures, the genealogies are EXTREMELY important. In fact, for some of those cultures, the genealogies themselves are what validate the truthfulness of the Scripture.

Though we may tend to skip over these, as they're more or less culturally irrelevant to us, that doesn't mean that they're culturally irrelevant to all people. I'd encourage you to read the article below, which lends value to genealogies, and some of the other more "boring" parts of the Bible.

http://www.bereaninsights.com/article/bible-gem-772-another-boring-genealogy-luke-323-38

As David Morton says, just because you or I don't see the value of some information, doesn't mean that no one, anywhere in the world, at any time in history, might not have a use for it.

And what do you mean by "non-essential"? It is said that a trouble-maker once asked Rabbi Hillel if he could summarize the whole Torah while standing on one foot. Hillel obligingly stood on one foot and replied, "What is hateful to you, do not do to your neighbor. That is the whole Torah; the rest is commentary. Go and study the commentary."

You don't mention the "begats", which are commonly cited in questions such as yours. But they have proven valuable to people trying to establish a chronology of the Old Testament, to attach specific years to events.

The "Table of Nations" in Genesis 10, another long list of names, has proven valuable to people trying to connect Biblical history to secular history by tying people in the Bible to nations known from secular sources.

As to the descriptions of the furnishings of the tabernacle, perhaps we are supposed to see symbolic significance. Perhaps someday archaeologists will dig up these artifacts, and the descriptions will help to identify them. Etc.

Maybe Christians 100 years from now will find some information valuable that is of little use to us today.

We can't always know the exact reason why there appears extraneous information in the Bible, especially the Old Testament, but there are often discernible reasons why it was important at the time.  To us it seems extraneous, but to them it was not.

Let's explain through the cases you listed.

First,  the details of the ark. 

Only the priests on rare occasion could see these holy objects and then only briefly. As they had great symbolic value in representing the future Messiah and as each detail should therefore be pondered on by those ancient worshippeers, to somehow catch a heavenly view, typed out into future prophecy, the details may have been quite important.  To us, maybe not so much.

Second, the sixty six son's of Israel that went down into Egypt

Here we go, yes, some people went into Egypt, became slaves and were eventually delivered by Moses, so what? However at the time a promise was made to Abraham that the Messiah would be born under his lineage, and that he would be made into a great nation.  Now all the ancestral lineage of this family to which the Messiah would be born is important to those who followed it, because eventually it must be proven that Christ descended from that line. Yet in this case there is even more interest to those who later were delivered from Moses.  Was it not worth pondering on the facts that even in servitude to a foreign power that almost tried to exterminate the Jews to control population, yet from these few names over a million were taken out of Egypt! So even under these difficult situations the details of these names would shown to those people at the time that God kept his promise to Abraham.

Third, Nehemiah's list of families that returned from the Babylonian exile

To us again these are just names. To Israel at the time this was a great miraculous work of God delivering his people similar to the Exodus under Moses.  That each family retuning to Jerusalem was precious tokens of the prophets who foretold a remnant would return, Nehemiah takes care to record.  Not only would this might spur on other to leave their lives behind in Babylon and join the 'city of God' but to ponder on God's concern for each family and his fulfillment of prophecy to them. Use have kindled Jewish hope after the sorrowful despair and attach on their faith in seeing something they never believed possible, the destruction of the temple of their God.

So we see, what is extraneous to us, was important to them, and yet it still teaches us useful things today. Not everything was written just for us but God preserved a people of faith since Adam, and they needed many support not to be swallowed whole by a world under the Devil's command, who desired nothing more than to destroy and stamp out any remaining fragments of true faith.  it is a miracle like carrying a candle across a stormy sea, that a people of God, and the lineage of Christ was sustained from the call of Abraham until the birth of a Son from a virgin. Each supporting beam that carried these people fully to the Promise is precious, beautiful, natural, yet divinely rich. Just like Christ, who was a like a tender plant, and a root out of a dry ground, or like Aaron's rod, which seemed like just a dry stick, but became a living branch, budded, and blossomed, so the dry scripture actually rose up into a living support of God's loved people and reach far into the future to safely support the arrival of Messiah.

Answer to Implied Question

I believe every passage you have cited comes from the Old Testament.

They would be there because:

1. the NT wants the lineage, of both Joseph + Mary

2. to the Jews it was important to understand which tribe of Israel they descended from. Thus, they kept detailed genealogical records. (I believe these were later destroyed by the roman general Titus)

3. this is important to God. If one reads the book of revelation literrally, 12000 is taken from each tribe of the 12 tribes of Israel. In order to do this, we must maintain genealogical records

Answer to Actual Question

I would happily read a bible that had 1000 more pages, where 500 of those pages talked about how God created the universe (rather than the few short verses in Genesis), and 500 of those pages explained Revelation in more detail.

However, I'm not sure what that extra book knowledge would do me.

One could make the claim -- that supposed we had more details about the Flood, it would make the bible more real -- and more people would believe it.

However, pre-Flood days -- in Genesis 3:24

So he drove out the man; and he placed at the east of the garden of Eden Cherubims, and a flaming sword which turned every way, to keep the way of the tree of life.

so presumably, pre-flood, humans head towards the garden of Eden, and see a Cherubim -- having physical evidence of something super natural -- yet they continued to ignore God / sin.

Then, there were people in the times of Christ, ... who upon seeing Christ and his miracles, claimed Christ was from the devil.

Given all that, I'm not certain more detailed knowledge in the Bible would help "Christianity" more -- in that the unbelievers will continue in their unbelief; and as for the believers, 2 Corinthians 5:7 states:

(For we walk by faith, not by sight:)