But the most used token on Tron is only the USDT itself, its almost no one talked about another token if its related to TRC20 token. And the only function of the USDT token is for arbitraging between exchange because of its almost zero fee.
It is used because of the cost and speed of transactions, the rest does not exist, because functionally it is clearly very helpful when everyone wants to arbitrate between exchanges which both have the TRC20 network.