I posted something about this a while ago. It's getting better, and with places like bitrefill other gift card providers & all the exchanges offering credit cards it will get better still. Just slowly.
Big merchants can get reports about where their gift cards are purchased. So as they see more and more coming from places like bitrefill they might take a look and go hmmmm this could work. With PayPal now slowly letting merchants accept BTC / crypto how long till some do it on their own.

Credit cards are a bit different, the merchants might not know but the credit card processors know who controls the cards. How long till they go out and see that the BitPay / Coinbase / etc cards are being used more and decide to process crypto on their own offering it to more merchnats.

It's just inertia. It takes time to get it moving.

-Dave