That's because an unleashed dog can and will kill humans. Cats won't.
Or do you think that a convicted and unreconstructed murderer should be allowed to own firearms?
Though I live in the country, I keep my dog fenced in or leashed at all times. Why shouldn't cat owners have to do the same?
BTW, I live on a farm, grew up hunting, and have seen the damage that both feral & domesticated cats do to wildlife.
Although we don't shoot such cats, my dad and I have a half-dozen Havahart traps in which we quite regularly trap cats. The animal control officers come by and pick them up.