I can download an APK and install it on android. Why can't I use my iphone like I use my macbook?

An underrated question. The answer of course is twofold:

* Paternalism (Apple believes users are too stupid to be trusted to control their devices, and no amount of "I really know what I'm doing" confirmations could change that)

* Apple's biggest fear is being disintermediated by Google or Meta, the way WeChat did to phone manufacturers in China. An ability to side-load an app could allow a foothold for a powerful competitor who could wean you off of all their lock-in features in favor of an experience that would tie into a competing ecosystem.

Apple would like your macbook to be more like your iphone: applications only via their store, thank you very much.

But it isn't worth the bother; the macbook market is much smaller than the iphone market.