I promise you it does. Maybe not to you, that's fine, but side-loading is very much linked to privacy, and privacy is a human right
according to Apple (and I agree with their statement). Side-loading is linked to privacy because side-loading increases the attack surface for hacking, in all the ways it happens on open platforms. As cited by Apple that means apps can't be recalled, even if it's a hostile app that's exploring weaknesses in some iOS version. And e.g. governments can insist phones contain certain apps, no matter how privacy-hostile those apps are.
None of those examples are fictitious. Side-loading is linked to privacy.
That's great for you, truly, I see your point and we definitely agree consumer-choice is a virtue, but… there is a balance to strike, because what's easy for you to keep disabled is harder for citizens of regimes that demand side-loaded apps, harder for parents who get duped into installing all kinds of ****, harder for kids who end up with insidious apps that crawl their phone for all kinds of data, in short it's a dangerous can of worms to open up.
Apple has fundamentally aligned their phone to privacy, and it is very much not an open platform. It never were, really. With all due respect, because your points are genuinely understandable and relatable, I think Android or other open platforms would be much more suitable for the direction you desire. To be clear, I'll cheer if Apple opens up where it doesn't sacrifice privacy, they need to play by transparent rules and there's lots to criticize them and their way of handling things for. But I really hope they can keep a lid on their platform to such an extent that I don't have to worry at all about what apps my parents and kids install, or what apps people elsewhere are forced to install.