I have a friend in Little rock that got shot 8 times with a 22 and he went on to take down the guy who shot him. He now works for a private protection agency.
So yes, I have seen it. You are wrong. In a perfect world the perp would have shot him 8 times in the head. We don't live in a perfect world.
Now as to your question, shooting someone in the stomach with a 22 might hurt as you say but it won't stop them. They will walk away or kill you and then bleed out days later. You want a round big enough to stop them. YOu want a round that kills their brain if you hit them in the head. If you hit them in the torso you want a round that causes so much damage that it short circuits the functions of the body and makes them bleed out quick. You want to knock them down thus big rounds.
If you can't understand that then go for what you know.