Unfortunately, some folks like to pick on others. And some folks would be more than happy to sit down and pickpocket newbies all day long, just for the sheer malicious pleasure of it.
I suppose, though, you could have an in-game flag to \'allow\' pickpocketing attempts, if that is your pleasure. And if you pickpocket, you automatically \'accept\' all challenges from the opposing character, and they can attempt to kill you/cast spells on you, etc, and it automatically allows pickpocket attempts on you.
At that point.. caveat emptor...