His character never really brings anything. He's just always getting upset at people. He's a reactionary character; rarely does he ever do anything on his own, it's all in reaction to the other characters. Also, his bind with the characters is weak (storywise). Everyone else is so crazy that the whole "But we're family" excuse for keeping everyone around doesn't really work.

The show is funny but it's base is pretty flimsy. If the majority of The Office followed Tim (or if most of Curb followed the wife) the show's wouldn't work as well.