The casino must paying the tax for their business while the gamblers pay the tax for personal or their wins. But gamblers should pay the tax for their income/salary as a citizen.
The casino can actually handle the taxes themselves and just deduct it from our winnings - simple, right? But this applies only to countries with strict laws that make gambling winnings taxable. There are guidelines for this, and it’s transparent because it’s part of the law. If we ignore it, we could get penalized or even face jail time since, as they say,
"ignorance of the law excuses no one."