I suspect it's less costly for the merchant than a credit card transaction. I would not see another reason why Coop, Migros and al would push it so much under one's nose at checkout if there was no money in for them

Now I don't see why I as a consumer I should prefer it to a credit card - in principle the CC should offer me more protection, bonus points, etc.

For personal peer-to-peer transactions there's other systems such as Revolut that are more international...