It can be a way of keeping himself busy because outside is expensive and there is comparison everywhere.
So to avoid all this, he prefers staying indoors; it's understandable.

But then what's addiction? It's using something to the point where it could be harmful to you.

For now it might not be addiction, but when he keeps doing it, daily turns to weekly, weekly turns to monthly, then yearly, and finally he can't associate with anyone but just his gambling.

Someone said as long as he is just doing 1% of his income...my dear, from just doing that 1%, he will graduate because that's the only place he has fun, so he can do more to keep up his fun standard. It will turn into an addiction with time.

My advice is for him to add some other things, maybe learn things online like YouTube while avoiding outside things.