- OSX is only available on relatively expensive Apple hardware because Apple sets (high) minimum standards on quality and "official" OSX on shitty hardware would pollute the brand.
- iOS apps are sandboxed and the App Store is curated to protect users from scammy/spammy/malicious apps.
- OSX enforces code signing, again, to protect users from malware. It can be switched off by users who demonstrate clear intent and understanding of the consequences.
- Parts that are non-user-serviceable are usually that way to achieve smaller form factor and higher capacities. The reason for non-user-serviceable batteries, for example, is that batteries are bags of dangerous chemicals inside of heavy and thick protective cases. Making the entire laptop the "case" for the battery lets them get larger batteries in less space and weight. That it cannot be safely removed by a nontechnical user is a side-effect.
Your comment attributes a sort of "inverse FSF" religious sentiment to Apple, as if they make things closed and locked down just for the hell of it, because they believe in closedness the way Stallman believes in freedom.
Reality indicates that most of their restrictions are about protecting users who don't know better.... you're not going to "accidentally" replace your CPU. There's no legitimate problem that would be solved by whitelisting processors. Could they do it? Yes, but only if they exhibited some sort of fanatic obsession with preventing users from achieving what they want even when it serves no other purpose. Which would be stupid. Hence, it's as likely as Microsoft being run by lizard people :).