ME: Why are people so stupid?
HER: Because they can be.
Think about it: In the past, evolution would gladly show stupid people the door out of this existance. Now, homo sapiens have evolved to the point where stupidity no longer affects their survival ability.
I don't think this is a good sign for humanity.
Fortunately, there is hope. When they get too stupid (like being deaf, walking along train tracks, and text messaging on your cell phone, all at the same time), evolution is still there to intervene.