That is not what’s stopping people for paying for things in bitcoin. When you buy something in BTC you pay the equivalent to whatever you would have paid in the local fiat. And on the vendor side, merchant services often convert that paid BTC into fiat in the moment after the sale. What actually keeps people from paying for day to day goods and services in BTC is Gresham’s Law, the observation that nobody wants to pay for purchases with an appreciating asset, so long as there’s also a depreciating asset they could pay with instead.