I never wore one as a kid, and after many spills I'm still OK (I think...).
When I got back into it recently my wife MADE me buy one, and being a Yorkshireman and having spent £50 on one, I am damn sure I'm going to wear it just to get my moneys worth!!!
I get even better money's worth from my no-helmet which cost me nothing. Came off my bike and ran into things many times as a kid/young adult all without a helmet and all without anything more than scuffed knees, hands and elbows. None of the family wear them now either and the worst we've had is badly skinned knees and a cracked tooth with grazed chin. Can't see how a helmet would have helped with any of those. Had two hospital visits with head injuries though from tripping over on an uneven pavement and falling over on an icy one.