> I absolutely agree with this in theory, but in practice I'm not sure it would ever work because they just aren't going to put in the work to build and maintain APIs for things they don't care about, and there would be a very long tail of things to do (and sometimes those things are legitimately a lot of work). Call recording being a classic example.

I thought about this a bit and I think that at the end of the day, the entire OS is just a bunch of these APIs. And I do think there's even a market for these APIs, they just don't want to set that precedent, I don't think it has anything to do with it being a lot more work than anything else they expose. They already have some very privileged APIs you can bless some apps (e.g. think of MDM) except not for everything and in the case of the MDM APIs it's very difficult to use it as a normal end-power-user.