What is the difference between having dollars in my bank account and having USDT in my binance account?
The difference is that you can get more yield with your USDT by having nearly zero risk same as holding fiat currency. Most of banks are robbing your yield for their own, it's the reason people interested in keeping stable coin over fiat money in bank.
You will get the yield you deserve by holding your money.
It is the same money, and keeping dollars in a bank account feels a lot easier to trust; keeping USDT in binance requires me to also trust the Tether team, and why would I need to? Doesn't mean I do not trust them, but I do not have to trust them; there is no need for that extra layer for me. For people who need it, because they have to, I understand using it, but those are very few and not hundreds of billions of dollars like the market cap USDT has; all of those people bought all that many USDT for some reason that I will never understand.

Holding your money in bank is also require you to trust bank people while we have plenty of cases about bank people were running away with their customer money. So holding fiat or stable coin such as USDT posses the same risk, but USDT feels far more flexible and superior because you can maintain your balance anytime at the same tiem get pretty good yield.
I also give you an example why keeping fiat is also possessing the same risk in the picture i provided above.