Iowa has no law requiring helmet use but I can count on the fingers of one hand how many times I've ridden without one in the last 20 years. Always long pants and over the ankle shoes, although I do ride with just an Aloha or T-shirt rather than a jacket sometimes when it is hot. Although, after seeing those pictures of the "Road Rash Girl" last year, I've taken to gearing up much more often. Since this is the only melon and set of skin I have I've decided to protect it a bit better.
On the other hand, as a libertarian leaning conservative, I don't think the state has the moral or constitutional authority to require helmet use. Like the ABATE guys say "Let those who ride decide." Just don't make me responsible for their decisions.