Take a puppy from a breeder or the shelter or what have you. You get this puppy when he's 8 weeks old. You get him a crate. Potty train him properly. You take the time and effort to be consistent, teach him not to jump up on people, reward him for good behavior, do not reward him for undesirable behavior. Give him a purpose and let him earn his keep. Keep him for life instead of passing him around. This is how you get a good dog. A dog everyone will miss when he's gone.

Now say someone else that you don't know gets a puppy. They don't bother to housebreak him. They just let him potty wherever. They leave him home alone for long periods of time. He develops seperation anxiety and chews the couch cushions and the linoleum every time he is left alone. He is allowed to be the pack leader in his house. When the dog is on the couch, the people stand around or sit on the floor. If the dog engages in attention seeking behavior, everyone stops what they're doing and engages the dog, or he will make life a misery for everyone. The dog is never discouraged from territorial behavior, marking wherever he feels like it. Then the owner of the dog has a major change in their life, and cannot keep the dog anymore. They then "gift" this dog to someone else. Surprisingly the new owner doesn't appreciate this peeing, pooping, couch chewing, growling, aggressive, territorial little nightmare, even if it IS in a small cute package.