Hmm, I think you guys are taking the drop features on casinos too far, one thing I believe is that the drop which happens in casinos chat box was never designed to be something really important, or a kind of giveaway that should really matter, drops are designed as a way of rewarding users who spend their time on the casinos chat box helping other and probably sharing ideas on what to bet and game to play, it is also a way of encouraging other users to become and stay active in the chat too.
It seems there is a misunderstanding here! OP is not talking about
drops a.k.a chat rains which gives cents to those who are active on the chat box. He is talking about lotteries and free raffles where the winners get thousands of dollars. Such contests need to be transparent and the casino have to make it in a way that all the participants can verify the fairness of the results.
This is why I said it's better if a well known streamer hosts the event or simply use a
pf system.