I mean, you don't _have_ to install another marketplace for apps.
Having the ability to side load gives the ability to people to coerce you into installing things that wouldn’t fly under a single root model.
I do not feel that computing is headed to a good place in terms of privacy and I feel like giving the Googles, Facebooks, and spyware companies more levers to pull is going in the wrong direction. (Well, maybe the right direction under normal circumstances if the tech industry was more ethical)
System permissions aren't tied to the App Store as far as I know (same on Android). You still need to give apps permission to access your camera, mic, location, etc.
While allowing sideloading would bypass Apple's review process (which can be bad), if someone has that type of access to your phone, there's nothing stopping them from installing tracking/spyware apps from the App Store right now.
Tell your employer to give you a work phone then. No way I'm going to install work-related sw on a private device.
What sort of backward country do you live in where that's even remotely legal?
Employers can already sideload through MDM. If anything MDM will give them more control than just an app.
On Android (and Windows/macOS, to a certain extent), the OS asks you if you let <app> access/use <feature> independently of how the app was installed.
Also, can apps monitor your communications on iOS? On Android you can replace the apps that control calls, sms, etc, but that wasn't possible on iOS last time I used it.
I know there are downsides if they allow sideloading, but iOS is very restrictive and Apple would still control iOS. They can add more restrictions and fix flaws if needed.
Employers have enterprise certificates and ability to install custom apps on both iOS and Android, and they can do so while bypassing their respective app stores.