I do gamble every now and then myself, but I am for sure not addicted.
Although I know my limits, it's really hard to stop when you're down. You can't stand the fact that you lose money, and you want to play more to get the money back.
I think it has a lot to do with the uncertainty of the outcome of the gamble. There always is a chance you win it back, so you're chasing your loss.
I thoroughly agree with you, one should know their limits. If you gamble too many times, you will get addicted. It is like a virus which spreads in your body bit by bit, you need to put a cure to prevent it from growing. As for me, I gamble because it is fun. To elaborate, I always consider it fun to watch people's reactions; when they are stressed, when they are afraid of losing, when they messed it up and lose. Added to that, I want to win and get easy money.