Use of real dollars (USD) instead of stable coins (USDT) in an exchange!

Why cannot we use direct money in an exchange instead of using stable coins like USDT, UST, or USDC? For example, I usually trade with pairs like BTC/EUR (Here EUR is real money), ETH/EUR, SOL/EUR, etc., instead of using BTC/USDT pair. We can find many pairs with Euro but not a pair with USD (real money). Why cannot we introduce USD, similar to EUR, instead of stable coins where no one expects what happens to its peg to the dollar.

Can someone tell me the difference between USDT (Stable coin) and EUR (real money), especially in Binance? Am I missing something here? Thanks in advance!