People knows that Bitcoin is good for investment and not for gambling that's maybe the reason why people always prefer other altcoins or just used USDT because they know that this is more convenient crypto to use for this matter.
The BTC network now has such a low transaction fee that it would be more profitable to use BTC for deposits or withdrawals on gambling platforms than USDT. I think one of the reasons why gamblers still prefer alts more often is that gambling platforms and exchanges often set unreasonably high fees just for BTC transactions.
Well, you may actually be right, but for me personally, I do not prefer to use usdt for gambling because of the possible network fees casinos set for those who are withdrawing bitcoin, and to even say that bitcoin transaction fees have become do low that its better to use bitcoin over usdt, I would say that this completely depends on the exchange and network you are withdrawing usdt from or depositing usdt to..
For example, withdrawing usdt from Binance exchange to any wallet on Binance smart chain is absolutely free of charge, while also withdrawing usdt from Stake casino to any wallet on Binance smart chain network only cost $0.1 in withdrawal fees, this is way more cheaper than transacting in bitcoin, and you even get faster network confirmation too compared to bitcoin.