Re: Depends on developer
If app stores were banned from taking any cut from subscriptions, what stops every app that isn't free from changing their price to $0 and going to a yearly subscription model? Then Apple and Google get nothing for operating their app store.
Based on Apple's margins for their app store, if they took a 10% cut instead of 30% they'd only break even. Obviously if they took a 0% cut they'd lose billions as none of their cost of running the store would be recouped.