Investing in a casino is a massive risk. Even casinos that once had a great reputation have recently had many problems, like FreeBitco.in. There were also other casinos like BitDice and Betnomi, that exit scammed or disappeared under suspicious circumstances.
Investing in traditional assets is one of the least risky ways of earning passive income. That is not always an available option so people turn to crypto. If you invest in a decentralized platform, it is best to consider how well audited and trustworthy they are instead of just apeing into whatever is promising to give you the highest yields.
Just hodling Bitcoin is also a very well known strategy that is proven to be very profitable over a long time.
Ofcourse every investment comes with the risk for our capital so we can't say any kind of investment is 100% safe no matter what. What you are saying is true as well casino investment is not safe either but comparing to staking it looks like a better plan to me cause there are some casinos which still allows bankroll investment while maintaining their reputation however it can change at any moment that is the risk behind holding our assets in a centralized platform.
I agree, simply HODLing is the best possible thing to do with the bitcoin but some traditional investors are not used to keeping their assets in their own custody they always like to take the game even though it doesn't worth the risk/reward.