Why do men shave their heads?

I can think of the following reasons (not in order):

1. because they're going bald and they've given up on hair
2. super low maintenance - no haircuts - no shampoo
3. it suits them and girls like it
4. it suits them and guys like it
5. they joined the army
6. lost a bet
7. they like the feeling of bare skin and being touched there
8. they enjoy the act of shaving their hair
9. they have a fetish for haircuts or headshaves
10. they're addicted to haircutting
11. they have a hair-phobia
12. they are monks or for some other religious reason
13. they wanted to see if there's anything underneath