If you had the option to sideload apps, Facebook might have pressured you to do that (and leave them free from Apple’s oversight) or lose your friends. Because

If you had the option to sideload apps, Facebook might have pressured you to do that (and leave them free from Apple’s oversight) or lose your friends. Because you can’t, Apple was able to have privacy controls imposed upon them kicking and screaming. You may argue this argument is wrong, but it’s not like it is totally incomprehensible.