Disease is something that requires us to take medication given by a doctor to cure it, in contrast to gambling that is only bad habits or bad hobbies that continue to be done even though they know it is bad. Addiction in gambling cannot be cured by medication given by a doctor's prescription, to eliminate gambling addiction we only need to leave it in any way you can, so you will slowly get rid of your addiction in gambling.
But medication help is more important to save someone when they are in serious addiction which can be considered as disease? There are different kind of addiction and also in different levels so most of them no need medical help but psychological advice will be much important when someone want to recover.