...I believe almost every trader make use of USDT becuz it is available on almost every crypto exchange, but I can't say the same for BUSD which is only listed on Binance exchange now, maybe exchanges will consider listing it when the demand for it grows.
You are wrong, BUSD is not only traded on the Binance. To see where BUSD is represented, you need to go to
https://coinmarketcap.com/currencies/binance-usd/markets/ and at the very bottom of the page, click on "Load More" to see the entire list. In addition, BUSD is indispensable in the Binance Smart Chain.