Arbitrary Apple rules. Apple decided that "physical" goods & services in app purchases don't get taxed (e.g., clothes, uber rides). Digital goods do because they feel like they can get away with it which is why you can't buy eBooks from Kobo or Amazon on iOS, can't buy or rent movies from Google on iOS. People will tell you this is for "safety" and to keep you from getting scammed but there's nothing stopping malicious actors from creating apps that promise to ship physical goods and just don't. At least with digital goods you should get whatever you pay for immediately after purchase.

But Apple doesn't take a share of Venmo or PayPal or Zelle either.

And Patreon sure feels a lot more like those -- you're sending money to a creator.

Sometimes you get extra content, but sometimes you don't.

The line is wherever Phil Schiller fucking says it is.

Whether Apple believes it can strongarm the related companies.

That's the reason why Kindle doesn't sell ebooks on iOS

Apple is threatening to remove the Patreon app if they do the same.

Subscriptions I expect....

Whatever you get as a Patreon patron isn't typically a physical product, unlike something you buy on Amazon (generally speaking) or a physical car ride. It's closer to a Netflix or a newspaper subscription, and Apple wants 30% of those too.

Some Patreons I subscribe to do include stuff like postcards, signed posters or prints, so it's not quite as black and white

The line is "can you use the purchase solely in the app distributed through Apple's infrastructure". I think their fee is outrageous, but that does seem like a defensible line.

Except they're stepping far over that line! You can use a Patreon subscription on all platforms, same as a Spotify or Netflix or Kobo... and yet they want a cut even when they have no part in the payment processing. Totally indefensible imo.

No, I think you misunderstand. It's not "can you use it elsewhere?", it's "if the user chose to, could they use the purchase solely inside the context of the Apple ecosystem?"

That is, if someone wants to, they can use Patreon's iOS app, not interact with Patreon in any other way, and get all of the benefits available to patrons.

I do wonder if a workaround here is buying a physical postcard from a patreon creator that comes with a free monthly subscription. A 50c mailed card would be cheaper for any subscription above $2.

I'm not sure you'd need to ship it. You're buying a 1/100,000 share of a physical postcard that exists at the Patreon offices. You can visit the office and see the postcard displayed out front under glass. It just so happens that buying such a postcard includes a free month's subscription to a Patreon creator.