The problem is the less informed you are, the less you are likely to actually do that. Greater knowledge causes people to question the limits of what they know MORE, rather than less. In other words, along with being educated and knowledgeable on any given topic comes the awareness that one doesn't know everything.

This is why people are are very skilled and informed tend to consistently underrate their own abilities when asked, while people who are not skilled or informed tend to consistently overrate their own abilities.

And people tend to become informed (in reality, not just their imaginations) on various topics BECAUSE they are the kind of people who probe and seek out information that they don't already know. So there is probably also some personality type self selection going on, as well.

Dunning–Kruger effect - http://en.wikipedia.org/wiki/Dunning%E2%80%93Kruger_effect