They're something that most people are actually using, allowing the marketplace to actually conduct commerce and exist.

And again, how do credit/debit cards—which are centralized systems—satisfy the proposition of a decentralized market?

"And again, how do credit/debit cards—which are centralized systems—satisfy the proposition of a decentralized market?"

They allow the market to actually exist, by using something that the people are actually using.

But a decentralized market does exist with cryptocurrencies.

And credit/debit cards aren’t decentralized.

Doesn't matter. That's what the majority of people are using; so if you want the marketplace to actually be able to serve people, and get them to actually buy stuff, you need to support them.

Not if you actually want your marketplace to be able to, you know, sell stuff to people.

Clearly not for the people using it right now.

What benefit does this actually give me in my everyday life where I don’t need to buy toilet paper anonymously?

Are you asking why someone would want to transact anonymously?