Are you saying we shouldn't really wear seatbelts while driving?
It's a question of acknowledging the risks and taking appropriate precautions, nothing more.
How you estimate your chances is up to you of course, but statistics have already proven that helmets are very useful in preventing TBI's (traumatic brain injuries).
Not falling would be the first thing to consider, wearing a helmet when you do, is the second...
You can exaggerate all you want, but you won't convince me that the small effort of wearing a helmet outweighs the risks.
PS, one of my best friends was the only one in his car NOT wearing a seatbelt, he was the only one that did not survive the crash, on the evening of his 21st birthday.... how's that for a dramatic example? ...
Spend those 70 bucks on a helmet, you know you should.