In Poland fees are capped at 0.3% for credit card, 0.2% for debit per EU. Which is why generally in the EU you don't have the insanity with credit card loyalty programs.

Only the interchange is capped. The merchant has to also cover network and processor fees. And then there are some uncapped transaction supposedly so the fee covers this risk. Comes out to 0.6-0.7% for a smaller merchant with the card present.

One person’s insanity is another person’s interesting puzzle and optimization problem.