And if you've ever used CC on Windows the usability difference is night and day.
CC aside, the designer community is moving towards independent applications. All of which initially launch on macOS, and in the case of Sketch (a product I use all day every day) they stay on macOS.
Developing on windows is a nightmare too. I remember the days in college when I couldn't afford a mac and wanted to do some rails dev on my windows machine. That was motivation enough to use Ubuntu. That doesn't even cover the fact that XCode only works on macOS.