When I start betting, it was a local bookmaker I used and they don't accept deposit in crypto, just in fait which was our local currency via bank app transfer or card debit. I started using crypto casinos and bookies few years ago and I doubt I have spent more than $20 worth of Bitcoin to gamble, the truth is that I prefer to deposit USDt than Bitcoin.
People that are using USDT to gamble may prefer to hold USDT instead which is not a coin of value as it is only pegged with dollar. Gamblers will most likely lose and that is not bad at all. I also noticed that I do not like to use bitcoin to gamble, I prefer to hold it instead while I use USDT to gamble.