Why do people steal other folks' pets?

Philippines
September 14, 2010 7:01am CST
My friend's dog is missing, and I suspect that it has been stolen since it's a really pretty German Shepherd. Plus, this isn't the first time that the dog got lost (they later found it at a construction site nearby on a leash that is not even theirs) and they've already discovered a couple of ploys some people try to do to steal their dogs. Why do you think they do this?