I can sort of understand this decision because once you choose a platform we are locked into Apple's will but I don't ultimately agree. Apple's platform isn't a monopoly, you can choose other platforms and you can also change platforms therefore Apple doesn't has a monopoly to abuse.
They do abuse their position but they aren't a monopoly and while they aren't (something that will probably never happen) a monopoly they should be allowed to design their platform however they see fit (although security and whatever is a false argument, the Mac has always had plenty openness to no real detrimental effect of its security)
Locked in is such a weak argument. Most users play games and use free apps and listen to music. No problem switching to another phone if you are willing to spend some time. The difference with Apple is that there is no friction experienced by staying within the ecosystem.
If someone does not the terms of the store then don't use it or buy a different phone. This "problem" is self-inflicted.