Much of the reason why people don’t go beyond the first level is simply because they lack the time. I’d love to know everything there is to know in the world, but no one can do that. No one has the time or mental capacity. Few enough people have interest or cause enough to learn that–for example–Abuja is the capital of Nigeria, let alone why it’s named that, how it was chosen to be the capital, etc. People usually only bother to look into the second level if the topic is something of significant personal interest or relevance.

As you’ve correctly observed, however, the truth is not always what gets written in encyclopedias and textbooks. What gets taught to children in history, science, or language classes isn’t always the truth, or at least, not the whole truth. There are several reasons for this, some of them simply practical like lack of time and resources to give a sweeping, penetrating analysis of the universe to every child growing up. But there are other sociopolitical reasons as well.

It is the nature of most world governments to cultivate a certain mindset in its citizens. Governments do not usually like the thought of people disagreeing with officially-held positions. Since those officially-held positions are frequently distortions of the truth if not outright falsehoods, most governments subtly attempt to instill a “Don’t question things too much” sort of attitude, the vague sense that “If something is officially considered true, then it’s probably true, and even if it’s not you’d probably better just accept it as such because otherwise you’d be stirring up trouble.”

For better or for worse, a lot of people grow up believing that. This is true of most countries in the world, including the U.S. I like the U.S. and believe it is a country which offers more freedoms to its citizens than most countries of the world, but the American government has a partially-concealed agenda like any other bureaucracy.

The real truth, as you’ve observed, doesn’t lie in officially-documented records. It lies in the hearts and minds of people. The result is sort of like being in Plato’s cave: We see the shadows of reality, we see the effects, but not the causes. We have a pretty decent idea of what’s happened, but we’ll rarely if ever know the full story of WHY something happened. This is, regrettably, just a part of life. Even in our present day, despite the Internet making more “information” more accessible to more people than ever before, the information that we get is filtered by opinions, circumstances, and gaps in knowledge. The nature of information and how people interpret and propagate it will likely remain about the same regardless of whatever changes occur in the technology used to spread that information.

I’m often discussing on subjects like this and many people don’t like or don’t want to get on a next level. As soon as I realize this I do stop arguing and tell them: look at the facts, get into detail, get experience and the discussion stops immediately.
On the other hand as a I’m subject to this way of thinking too, I welcome the benefit of doubt and contradiction and check things at least quickly on plausibility: do they fit my experience? And if there is doubt and contradiction I do ask for the next level e.g. scientific evidence of dowsing.
Once you are aware of these levels you can juggle with them and do profit from all of them: simplification on the one side and the hard facts on the other side.