Ok, suddenly the casino you're playing asks you for proof of income to be able to withdraw your winnings and to keep your account in good standing, your bankroll every month is $500 and you provide proof of salary that you are making $500 net every month, will they accept that proof will they accept that you are putting all your salary for gambling, will this violate the principle of gamble for fun, because you are working to gamble based on your proof income.
Well it's hard to believe that you're using your whole salary for gambling. How about your other expenses? Are you going to rely on your gambling winnings to have such decision to gamble it all? Anyway, I don't think there's a casino who would care on where their players getting their money to deposit. Isn't it good for them that their players are consistently playing and spending their money on their platform? Because it's none of their business. But is this based on your own experience in a specific casino?
I think he was only using that as an example because no one in their right minds gambles all their salary and we don't even have a full salary because there will always be deductions for it. Proof of salary/income was only one of the options that some casinos are asking for their KYC verification.
They need to ensure that all the money that is being put on them are clean and doesn't came from illegal activities. I think this was also being ordered by the government so even if they like to cater all types of players to be able to earn more, they can't possibly do it. Earning small is better than not being able to operate and earn nothing at all.