If Apple clamps down on 3rd party apps to the point where it is no longer serving its user-base, the user base has many good alternatives, and Apple would lose business.

I think the Spotify example is a good one; if Apple kicked off Spotify, there could be millions of people switching to Android just because of that. Apple might love the idea that only Apple Music should exist on their iPhone (in fact they was kinda Steve’s original vision) but they can’t get away with it specifically because they would be clobbered by the competition if they tried.

Even as (if) Apple’s reputation shifts away from “walled garden that protects you from junk and malware and spyware” toward “overlord trying to control what you can buy” this causes some users to leave.

As long as there’s viable competitors, I’d rather let users vote with their wallets. This is actually the best way to give people the choice of which system you would prefer using. If the fully open system is preferred by most users then most users will choose that product. But because there are actually huge trade-offs and very hard unsolved problems with a fully open system, it’s important to provide consumers both options.