The only thing in common between gambling and MLM(ponzi schemes) is that the people involved in those industries lose their money.
I don't see any other similarities.
Gambling is based on luck(assuming that the casino is legit and doesn't scam players with rigged games), while MLM is based on trying to find more people to buy a shi*ty product/service, that ends up being complete scam. Can you find any other similarities?
Many casinos have referral/affiliate programs, but this isn't the same as MLM marketing. The product prices is MLM marketing are high af, as well as the commisions, while in the gambling affiliate programs the average commissions per referred customer are pretty low.