You don't want to see the Australian interchange rates…
And yes, "it can only become cheaper" has a much lower cognitive load than US style payments where the advertised price is just a lower bound.
I think the real problem is that merchants don't want to discount cash, because it still costs money. So now they can have their cake and eat (some of) it, too.
(Personally I think it’s fine to charge any which way you want as long as your terms are clear. But I think this answer makes clear it’s not so obvious as you suggest?)
https://www.bankofcanada.ca/wp-content/uploads/2017/11/boc-r...