Bitpay allows you to use bitcoin with a VISA card https://bitpay.com/
Some merchants accept it, Overstock being a famous one.
Also I think your missing the biggest use case, abet one that isn't frequently discussed, and it is that crypto currencies are by far the best digital payment solution when it comes to the time it takes for transactions to clear. There is no dispute process, and there is no waiting on the fed for their ACA system to clear your transactions. However, I think a lot of people prefer credit cards for cash back and to have the option to charge back, but certainly cryptos are better for sellers (and potentially will give discounts to those who use them in the future).
Isn't paypal much faster than crypto currencies at doing the same? The normal banking system is quite slow (in part for good reasons) but the digital currencies that came before the crypto currencies are much better at this already, and better than bitcoin will ever be.
PayPal transactions never really clear. You can probably reverse a 3 year old PayPal transaction...
But Bitcoin payments are irreversible after only 1 hour. There are no other systems that accomplish that online.
You're correct: if crypto currencies were digital currencies there would be no advantage. However, crypto assets are decentralised & resistant to censorship. The power shifts away from the nation state (& Trump), & toward individuals.