Because the smarter you are, the more you're aware of how little you really know. One of life's most important lessons is to take a moment before you speak, because what is very true for a lot of people is that the smarter you get the less you speak.
To the girl that sleeps very little but thinks a whole lot. Einstein refused to sleep more than 5 hours at a time. This brain of mine has a lot to think about that simply can't fit into an day. -- Fun Psychology facts here!