Why is cracking knuckles addicting?

I have been cracking my knuckles for a couple of years now. and yes i do think it is addicting. i do it self consciously and i don't know how to stop. I've tried MANY MANY things and it won't work. i find myself doing it. but i am still trying. i have read about people actually stopping and i am gonna be next. because i think my finger\joints are getting fat from it. It is a habit but i think i habit could be addicting and this one is. so yeah. it is kinda sort of addicting. It's a nervous habit and ALL of us have something we do as a habit. Some people play with their hair by twisting it, some bite their nails, while others knuckle crunch. I've known people who pick their skin or pick their feet while watching TV and some people bobbing their legs or foot constantly while sitting. Here is a good way to stop from cracking your knuckles, but I have to warn you it hurts! Get a large elastic band for each wrist. Wind it around until it's just resting (not cutting off the circulation) and when you feel you are going to crack your knuckles take that suckah of an elastic band and stretch it and let it hit your wrist! After a week believe it or not you have tricked your subconscious "not to crack your knuckles!" One of my girlfriends stopped her nail biting by doing this.