You've never seen it as a checkout option? I mostly agree with you (nothing's been revolutionised) but I've seen plenty of web shop checkouts where I'm just buying something normal/not because they accept crypto (which I didn't know beforehand) and it happens to be an option. I assume the payment provider just converts and gives them whatever currency they want, just as they do for global currencies already if they don't want my Great British Pounds for some reason.