The real problem of Apple Tax–it ruins value-chain

This is a bit unfair.

You might say that Apple makes too little investment in the app store now, or that it is full of dark patterns (note that they hide the search box on both the Apple Store and Google Play to push you into whatever is being advertised today), etc.

You can't say they make 'zero investment'.

It is like the banks with the credit cards (who take less than Apple.) They take 3% off the top and that goes to various nontransparent places such as reward programs, risk management (say you don't pay your card or you have a dispute with a merchant, or the merchant doesn't pay their debts, ...)

The banks do something of value, we just don't know exactly how much.