I shave my head because I'm going bald and I look like bozo the clown if I let the back and sides grow.
Also I live in the US south, and when I speak it sounds like cornbread.
SO MANY TIMES people think I'm a person they can be racist with or like you said, regurgitate what they've seen on the news. When I'm working, as a general contractor, it's even worse with the dirty stained khaki Dickies work pants and bright neon yellow or orange shirts.
If I grew my hair for long enough I could do the hippie side and back pony tail.... but I really enjoy not having to do anything with my hair. I had long hair all through highschool and for several years afterward. I miss how it looked, but again I really really enjoy not having to worry about it.