Some gamblers are smart enough to stop playing after they have experienced a huge win, or think that they're losses are no enough to deter them from gambling. Gamblers are always one decision away from being a 'smart' gambler, and most of them take the obvious and easier choice which is to keep on gambling.
I've not seen a gambler that left the casino and never returned, even among my friends, they might leave for a while and return again, maybe not as often as before, but they still gamble.
When you've been a gambler, you'll always regain a gambler, especially when you still keep gamblers as friends, one way or the other, you'll return to gambling. The only exception is that if you left an addict, you'll likely return a more responsible gambler since it's expected you've learned your lessons.