If pickpocketing isn't a realistic challenge, then I can't play a thieving character who is challenged by stealing. I want there to be a risk/reward relationship so I have to make judgement calls on whether to steal or not steal.
Your point is a complete non-argument. You are completely overlooking that a game needs to be designed with an eye on both mechanical challenge and narrative internal consistency in order to create a convincing world. You don't put the BFG in the first room of the Doommaze and then tell the player "so what? Just don't use it if you don't want to". That's a terrible design attitude to have.
Have you tried pickpocketing Auntie Ethyl in the grove?
