If an iPhone is your home, installing an app is inviting someone in. Apple demands they approve all your visitors, doesn't trust you to do it yourself. They say it's to stop criminals but it's really to stop competitors, charge tolls from the rest. https://www.theverge.com/2021/11/3/22761724/apple-craig-federighi-ios-sideloading-web-summit-2021-european-commission-digital-markets-act
I wrote about this a few months back, and likened Apple's approach to a nursing home. Some people need the extra care a nursing home provides, so it's great they are an option, but most adults don't choose to live in one. https://puri.sm/posts/the-future-of-computers-the-neighborhood-and-the-nursing-home/