Mommy needs a helmet not to protect mommy's head, mommy needs a helmet so that her three year old son doesn't decide that he is not going to wear his. No offense, really, but I am betting that you never had kids in the 1-4 year age range.

As for "cool" factor, it cuts both ways. As soon as the majority thinks that seat belt/helmets are necessary, both risk compensation, and the coolness factor reduction in behavior become a nonissue. Noone now thinks about whether or not there is a seat belt on, it's simply on, as it has been for the entire life of the individual.