I don't know if it is addressed before but my question is why eXch does not have USDT on tron network too ? Or is their any plan for that ?

I think most of the users will prefer to convert into USDT using tron network because it saves a lot of fee. It won't be feasible to convert to USDT on ETH if the amount is less as there is will lot of tx fee involved in moving the USDT on the Ethereum network.