[zaphoyd]

On the Mac, where the App store is not required, a great deal of software is not in the App store and as a result the user does not benefit from App Store policies for said software. By forbidding sideloading, it forces developers to meet the App Store standards or not play at all. There are developers whose software is present on the iOS app store but the companion Mac app is not.

I don't like the complete lockout either. I like being able to run my apps on my device. But it is most definitely true that the ability to sideload apps results, in practice, in some developers opting out of providing App Store protected apps in favor of asking you to sideload.