Earlier quoted context omitted.
It could be useful for lots of folks that know UIKit inside and out but haven't dealt with AppKit before.
But a Mac's interface is not an iOS interface. There are different constraints and different best practices, and sometimes completely different widgets. To make a decent UI, you have to understand the native platform.
The ability of a stopgap measure such as this is a good way to let established iOS players test the Mac waters without a huge investment.