To be fair, you can sideload apps on to your iPhone, it just that if you are not part of the Apple Developer program you'll need to resign them every seven days.
I am an Apple Developer, but that still requires me to use open source apps, since I have to compile it myself. Also it's a lot of effort.
It would nice if I could just go to a web page, click a link, and say "load this app, I accept the performance/security risks this entails". Like I do with my laptop.