I have wondered the same thing. I can understand being in a bind and needing money but a good dog is usually good for the person that trained it. Alot of people will go buy a dog and think just because it's "finished" it will hunt for anyone. Then they end up culling a perfectly good dog because they don't understand each other. I have never once "culled" a dog. I gave a good squirrel dog to a friend one time because I had 3 good squirrel dogs and he didn't have any. A dog wants to learn. You just have to spend time with them. A good dog has to be made not bought. I know a guy that bought 4 squirrel dogs out of some very good stock but he ended up "culling" everyone of them. They would have made anyone with a little common sense a great dog. I'm just saying, if every dog you get or the majority of them turn out to be "culls" maybe you should got back to square one.
I agree, sometimes a perfectly good dog gets ruined by the new owner. Other times the dog will need to accept you as the new master before it will hunt. Mtn Curs are bad about this. It seems to be worse if the dog tends to be a little timid. These kind of dogs do not need harsh disipline because a little goes a long ways with these type of dogs.