That's likely the effect of gambling addiction as no gambler would just gamble all day, sometimes this addiction would not allow us to sleep since we don't have a peace of mind, therefore these addicts will try do drugs and drink so they can be calm and they'll be able to sleep when they are too drunk.
You talk like all gamblers are also alcoholics. While this may be true for most of them, I think not all are like this. There are also gamblers that know what they are doing and not losing control on anything. Not on their health, not on their finances.
It is possible to be a responsible gambler. You don't need to lose your health.
Maybe in gambling for them alcohol, drugs and drugs is normal when playing but this is for irresponsible addictions because their emotions are out of control so what they want will be done to calm their minds so this is what makes health not improved even always lead to ration.
Gambling can still be done consciously and I think this has been done a lot here, I'm sure the gambling lovers here will be more responsible for how to play their money in betting.
Some people are using drugs to keep them calm when gambling and that's one of the signs that they're very impatient and already a gambling addict. Also, it'll lead to the worst situation, which is he might get addicted to drugs or alcohol too.
So every time he's playing gambling, he'll now look for those partners of gambling, which drugs and alcohol and that are massive destructions to your life.