I also thought the same until I made a USDT transaction a few days ago.
I had some USDT on ethereum network and some on tron network. I wanted to make a transaction and I expected TRC20 transaction to be cheaper, but I was wrong.
I checked fees on both blockchains and the fees was much lower in ethereum network. If I remember correctly, the fee for making a USDT transaction on tron blockchain was around $3.5 worth of tron while on ethereum blokchain it was around $0.4 worth of ethereum.
One thing that bothers me is that the tx fee on the tron blockchain has been increased. If you remember usually we used to pay 1$ fee to transfer USDT on tron network but these days, the fee has been increased drastically. Other blockchains are focusing on reducing the fee but this seems to be opposite with the trx chain. Don't know the reason for this?
Anyhow, bet105.ag only supports Ethereum blockchain for USDT, so not much concerns for the gamblers at this platform.