To protect the brand. Sure there might be slightly less profit for mozno due to the cost of replacing the card but it’s probably worth it. They are still making a profit albiet a smaller margin but profit all the same.
I don’t agree with mozo forcing more waste though as it’s still the customer’s decision as I see it as the customer’s waste.
When someone goes out to a bar (Plus) they don’t get to keep the pint/wine/cocktail glass (Plus card) to use at home (regular monzo). For your drinks at home you back to using your regular glasswear (hot coral card).
The bar isn’t being unethical because you can’t keep using their glasses at home and thus more glasses have to be made.