Don't let Apple PR fool you into thinking commercial decisions like this are anything like principle based :-)

If Amazon, Uber and Lyft drop iPhone support, people will atop using iPhones and that's pretty much the only reason Apple doesn't charge them a commission.

You think people will stop using iPhones because a ride sharing app goes away?

Ever wonder what would happen to Uber and Lyft lost iPhone customers as a user base?

They would both suffer drastically. If it came to that, I’m sure other big companies would join in as well in an attempt to punish Apple ie Netflix,Spotify, and Epic Games

That could definitely put a hamper on new iPhone sales.

What about e-currency? They don't take a cut from coinbase.

What about Patreon?

Patreon probably gets by because a lot of Patreon rewards are physical items, or other services performed by the creator where Patreon (and by extension Apple) cannot guarantee will be received.

Meanwhile an app whose subscription model is “you get access to digital content” falls square within Apple’s IAP rules. I’m rather shocked Fanhouse got approved in the first place.

The fact that Fanhouse got approved means Apple's rules are arbitrary.

Not so arbitrary. If you are big and in the market Apple is not interested in, you are safe. Once Apple wants to step into that market, you should be careful (ex: spotify).