I'm fan of the Apple's AppStore model, I like it and think it works great and Apple's commission is a nonissue for the most use cases(it's issue only in low margin trades), however I'm afraid that Apple's control over the device risks governments making Apple their police. Apple limiting AirDrop in China is a very bad sign of what might happen if the rest of the world follows China's totalitarian path. Even in the US, which was supposed to be the land of the free, there are talks about banning apps.
That's the primary reason I want side-loading.