Yes, it's true that some casinos cover network fees and others don't. I don't think that's a problem, although we do prefer casinos that cover the fees because they save us money.
As long as the casino operates well, meaning it's trustworthy, then we're comfortable with that. What we're looking for is a trustworthy casino, but it's a plus for casinos that care about their users, especially with the many bonuses they offer.
Casinos and other business only can cover blockchain fees if the fees are not too expensive. They can even cover expensive fees on blockchains when fees only suddenly become too high for a while. However if things won't get better, no companies are able to cover it for their users forever and they must change their policies by increasing withdrawal fees before dust settles.
Withdrawal fees on centralized platforms are temporary and can be changed anytime so we as users must be ready for any change from them. We must be ready to pay withdrawal fees or even smaller fees if we use non custodial wallets and don't get any extra charged fees by any centralized company.