I live in a helmet state so that's how I got started wearing one. I do, however, commute 50 miles daily in a non-helmet state. It is not only leaving and returning to a helmet state that keeps me wearing one though. I'm more comfortable in a helmet.
One, it reduces wind noise.
Two, I don't find it hot in the summer, except maybe in a traffic standstill, and you're going to be hot anyway in a jam. Plus you can take it off in a jam. Another factor is I wear white helmets which reflect the sun's heat.
Three, at the speeds I travel I find it much more comfortable in a helmet. Maybe it's different for skinny folks, but when I get going at supra-legal speeds without a helmet (I lived in CO a while) my lips get mashed and flobble around, the flesh on my face gets pushed around like in those g-force pictures and when I look over my shoulder my shades blow off (well, not any more, I learned to hold them on when turning 20 years ago.)
Four, the general principle that there are two kinds of riders, those who have crashed and those who are going to crash. I was lucky enough to get one out of the way earlier this year (when you haven't crashed in twenty years you start to worry how it will be this time). Took a small diver stopping in a right turn merge - I could see that curb coming the whole time until I bongoed the side of my head into it. Wearing a good helmet, no problem.
I wear a full face helmet. Most of the year I leave the wind screen off, 'cause I like the breeze too. I'll tell you what tho, a windshiled feels just fine on 32 degree mornings and even better during 35 degree rains.
I started wearing a full face more than 25 years ago. I was watching a stunt rider jump some cars. He made the jump, but not the important part - the landing. He endoed and slid down the track on his chest and face. He got up and his face was fine - he was wearing a full-face and the chin bar and wind screen saved him from major shredding.
Where it is legal I might ride without a helmet in the city or for a jaunt down to the convenience store, but for commuting or pleasure riding it's a brain bucket for me.
