[fizgig]

I think the argument is that if helmets are not mandated by law, more people will ride. If more people ride, that will raise more awareness of bikers and their safety in relation to motor vehicle drivers. Therefore, in aggregate, the safety of the whole bike riding herd will be better.

Anectdata: I work on a large business campus which has bike sharing bikes scattered around. Helmets are mandatory (whether that's due to law or local policy, I am uncertain). My light whispy hair will irrecoverably look like shit after being subjected to a helmet, especially during the hot/humid months. As such, I opt to walk or drive more often than I would if I could simply hop on a bike for many on-campus jaunts for various duties.