...Yeah, some guys get bald spots early on. The unluckier ones start developing the bald spots in high school.
There is a reason there are guys who commit to shaving their head when young adults, and premature balding is one of the biggies.
Not that they'll tell you that, of course.
"Hair gets in the way of helmets" There are many alternatives, like wearing a cloth around the hair.
"Had to shave while in the army" Total buzzcuts don't leave the scalp smooth, and hair grows back at a rate of ~1 cm a month. Two weeks and you would see significant stubble.
"Underwent chemotherapy" Ok, this is possibly one of the few reasons that aren't lied about.