The game already encourages players to murder every innocent or not innocent beings for experience and you want to encourage them to rob and steal everything also?
Imagine the game being released and every single player's first decision is to be a crime lord because the rewards are so good compare to other civil skills, not because everyone have a thief heart but because the game encourages it. Sort of like the first game where the player just goes into every house and steal every expensive painting or jewelry, because books were expensive and you could read every book and it was so easy to steal.
Thieving is just one civil skill, it shouldn't be that much better than the other ones, I think it's not so bad in current state, know the npcs, steal what you need to give you an edge in quests and get out. (like invisibility potions or keys) I find sneak to be completely useless though, there is really no point in sneaking when there is invis skill.
