We have non reversible payments already. It's called wiring money. People generally avoid using it unless absolutely necessary, because it's expensive (much like bitcoin) and most of the time, it's not what you want.
Wiring money isn’t a great analogy. In the US it’s expensive for consumers just because banks can charge a lot for it, but ACH isn’t really more or less reversible (I.e., both are, to a degree) and is free. Conversely, in SEPA, wire transfers are free/inexpensive and in my experience people routinely use them for consumer payments.
The depository institutions themselves don't actually pay much at all - FedWires are about $0.033 to the DI. Some DIs offer domestic wires free of charge like my bank does.
SWIFT international wires do cost the DI more, but not several orders of magnitude more. I don't happen to know that number off hand.
Some retail banks charge a lot for wires because they can - people don't use them frequently (as to your point its not what people want most of the time) and usually only for bigger purchases so the fee matters less.
However, if this is something you do more often, banks offer steep, steep discounts over sticker.
