Why do dogs eat underwear or socks?

It's like what a wolf would do when he drags a bone away from the rest of the pack to chew on. It's his prize, and he doesn't want any other pack member to take it from him. That's sort of the same thing with dogs that like to hide your personal items like your shocks or a shoe. Unless you teach them that those are your property, he thinks that it's his and he can do whatever he wishes to them.