Originally Posted by
Doohickie
Sweat management, keeping the sun off one's head in the hot sun. The latter is optional for younger guys, but if they wear their hair very short or shave their head, or of they're bald, it's pretty much necessary (bandana, skull cap, something). Maybe because guys tend to get thinning hair in their 40s and 50s is why the OP notices this more with them.
I'm 31 and have been having this problem for 4 years now
I had a teammate in high school who shaved his head shortly before we went to a 3-day stage race in Arizona. He had little red ovals all over his lily white scalp by the end of the weekend.