I might get downvoted on principle, but I genuinely wonder and don't understand: why is it NOT OK for Google and Apple to ask for a cut? They have spent years and millions (if not billions) in developing the infrastructure, public trust and user base that allows developers to reach millions of potential customers in the first place. They provide some valuable guarantees that apps should follow that benefit and protect the consumer. I understand that bypassing fees is a way how to temporarily "have green numbers" and show savings on the quarterly report, but this is like a sugar company trying to sell sugar on the streets outside of a supermarket chain, because they don't want to pay a fee to the supermarket chain. It's their app store, their user base - why can't they make their own rules which benefit the consumer in the first place and not the greedy provider?

Again, I am genuinely curious what ethical principle am I missing here.