To be fair all it takes is for enough entities to exchange it between other assets. If you are in Europe, most stores won’t sell you anything for your USD unless you exchange it into euros (except some edge cases), so it does feel kinda similar in that sense except cryptos don’t really have a “home” country where they’re universally accepted (bar some nations whose own currency has so throughly failed they adopted it).

There are some services which allow you to spend crypto by simply doing the exchange for you at the point of purchase into whatever currency the store uses (similar to visa/MasterCard/your bank doing this if you pay by card abroad).

I’ll say ultimately though it doesn’t change a lot, the idea of crypto is great and there are some where the implementation actually yields something that could be a better money (truly yours, not controlled by a government or a company necessarily, low fees, near instant transactions), but in the end there are just too many of them and they rock the boat too much for the well established financial institutions that they’re just doomed IMO.

However, the technology itself I expect will end up being used against us by the ruling class in the coming years (i.e crypto currencies controlled by the government where they can set whatever rules they want on it).