I'm not suggesting that crypto replace any existing use for bank cards or apps like zelle or cash app. I'm suggesting that there are other payment scenarios where excusing systems don't fit, like a dispensary that lost access to a payment processor (hypothetical, not sure if this has happened) or a merchant wanting to avoid transaction fees. It's absolutely useless in 99% of all transactions, but it's not 100%.

Are you arguing that any technology that does the same thing as an existing one has zero value whatsoever?

I'm not anti bank or bank card, when those aren't an option crypto is a valid option. Ideally something without much for transaction fees, of course. Since prices are volatile, you would likely only purchase what you needed when you needed it.

This is wildly inconvenient, but remember this is a "banks are not an option" scenario. That's really up to the recipient. It could be a dispensary that got shut down by their payment processor, or another shop that wants to avoid the 3-5% transaction fee that payment processors charge. And yes, it could be something nefarious or illegal on the dark web.

To say crypto has no valid uses is simply inaccurate. For most people, though, there are better options like peer-to-peer payment apps (zelle, cash app, etc.) or just plain old cash.