There's no need to completely prevent non-certified content from being accessed, you just make it a second class citizen, e.g. by making installation more diffi

There's no need to completely prevent non-certified content from being accessed, you just make it a second class citizen, e.g. by making installation more difficult or restricting the access to native interfaces. E.g. you can increasingly fall back to distributing stuff that's incompatible with Apple's morals using HTML5, so customers don't need to switch devices to access some version of it. Barriers to switching are falling as more people are using cross-platform stuff (first and foremost, web content and apps) but at the same time they are increasing as people get a large portfolio of content that is either not available or that they haven't bought for other platforms. E.g. switch from iOS to Android and lose access to game X that's not available on Android, app Y that's available but you only bought an iOS license and, of course, convenient access to your collection of iTunes music and videos. Contrast this to a waning desktop era where most casual users seemingly only used and paid for three pieces of software (office, browser, something else) and had much of their other content in cross-platform containers (CD/DVD, MP3, Xvid, office files).