There's nothing magical about credit or debt cards - in the former case someone is vouching that you're good for the money in the future, in the latter someone is confirming that you have the funds already.

There's also no intrinsic need to use fiat for this sort of transaction. It is irrelevant whether the medium used is USD, bitcoin, or seashells, as long as the merchant and bank both work in that medium.  At least with bitcoin you have the option of cutting out the middleman entirely.

Comparing credit cards to bitcoin is pointless, because the two are entirely different (and not at all mutually exclusive).