To me it seems that you've just added one more intermediary than getting rid of them
Maybe. Or maybe he was going to be depositing some money in his bank, sending it to a bitcoin exchange, and buying bitcoin with it anyway. Whether he does that with $100 or $10,000, it's still the same process, and so these extra steps are trivial for him. It also opens the possibility of people purchasing goods from him with bitcoin, and him sending that bitcoin directly to his supplier, meaning no intermediaries at all for him.
USDT avoids price fluctuations and is more convenient than Bitcoin.
And also more centralized and less secure.