You do not understand because lots of apple users clearly have different usage requirements for their phones.
I tinker with stuff 8+ hours per day for a paycheck; when I'm using my phone, I don't want to tinker with it, I want it to just work, and my iPhone does exactly that. Someone has made a bunch of intelligent design decisions about the way things work— much better than with android phones— and I agree with them often enough that I don't care that I can't change them. My brain is busy; the fact that I don't have to think about changing them is great. It's an appliance to me. I don't try to reprogram any of my electronic kitchen appliances either, and I'm a software developer that used to be a chef. I'd much rather spend my time concentrating on the output than the tools. I get that it's not everybody's workflow— you do you.
I also really don't care if I can't install apps that aren't available through the app store. I use a teeny, tiny fraction of what is available through the app store... the chance of app store availability being a limiting factor in my phone usage is pretty much non-existent. I use a computer for everything I can't use my phone for, and it's usually better for those tasks, anyway.