He was a great earner and brought in a lot of money for Paulie and the rest of the guys. Thats mainly why his craziness was tolerated.
Plus, he tipped BIG. lol. THAT and also nobody could really tell where they stood with Jimmy. He was a smart guy! I have WISEGUY and in the book it states, "At dinner he could be the nicest guy in the world, but then he could blow you away for dessert."