I thought I read somewhere that badgers were raised in captivity in China and that the badger hair that you see in shaving brushes does not come from shooting and killing a badger but rather from shaving the hair off a live badger (as unpleasant as that task may be).
Still, I have to admit that the post above about badger hair just being rarer to find than boar hair makes sense.
If you haven't tried boar, by the way, you are really missing something. My boar brush makes MUCH better lather than my badger brush ever did, and yes, the boar feels a little scratchy on the face, but to me it's a good kind of scratchy and probably helps to exfoliate the skin.