Men to Boys

Why do men turn into boys when they are hanging out together?
A single male can be polite, look clean, dress nice, and be totally human. But put him in the vicinity of another guy (or his father) and miraculously he reverts back to childhood. Now his priority is Playstation games, shootem up movies, and alcohol (leading to attempts at sexual encounters after being lewd, crude, and smelling of beer & cigars).