I've seen at least one company use the Enterprise program to circumvent paying Apple 30%. One company I know preloads their app on an iPad, resells the iPad and associated hardware, and charges a subscription to use the app.
You bought it, you get to chose what code runs on it, and DRM shouldn't be used to prevent that.
It is not because the apps were nefarious.
The Apple Enterprise terms simply state you cannot distribute to the general public. It doesn't matter that the app was terrible, the violation itself was much more boring.
The FB app targetted young people and literally installed a VPN profile that routed all internet traffic through Facebook servers.
Essentially full network packet-capture of everyone who installed their app. That's the definition of nefarious.
The enterprise certificates were revoked primarily because they violated the #1 rule of the enterprise account - do not distribute outside of your company.
As long as user consented, the app should be allowed to do anything.
Amazon Prime Video, Netflix, Spotify, DirectvNOW, Sling, and quite a few other apps don’t allow in app subscriptions. There are others that you can subscribe to inside or out of the app.
App store guidelines ban having a link in your app to an external subscription website. They also ban "calls to action" that encourage customers to purchase non in-app purchases
As opposed to the 60%-70% that software developers use to have to pay retailers?
According to what Rebelgecko said, it sounds like the only reason Apple's service has any value at all is that they artificially restrict any possible competing payment methods on their devices.
There is nothing wrong with Apple charging a 30% fee on App Store Purchases, or purchases made in-app via Apple's framework. I suspect just about everyone will agree on this point.
The "extortion" part is the complete and total ban on purchases made outside the App Store.
Edit: This was sarcasm.
But apple? Nope
There are a lot of problems with Android, but an appstore monopoly isn't one of them.