Your app updates go to everyone, even if they've stopped paying their subscription.

So it becomes really tricky to sell a subscription on iOS where, once lapsed, the user can continue to use the latest version available at the end of their subscription.

One way to do this is to have feature unlocks based on a timeline (Working Copy, an iOS git client, does this). Where users continue to receive a subset of features but some new features are locked behind a yearly upgrade payment. This requires littering your codebase with checks that certain features are unlocked based on the user's latest yearly purchase.

I'd love official support for the JetBrains / Sketch subscription model on iOS. As a developer, I would feel bad locking my paying users out of features they paid for just because they stopped subscribing. But I also really can't be bothered spending months developing a robust in-app-purchase feature locking mechanism to work around Apple's limited set of purchase options

Now if I'm working for someone else, then sure! But, say, an author, who can no longer edit their old works for a republication? Not a chance.