macOS has several types of users
1) final cut users. As it's a Mac proprietary software, you have to use it on a mac. It's userbase getting smaller as time goes by. Some of my friends have migrated from final cut to Adobe premiere/after effects and eventually even swap to a windows machine. Personally I prefer davinci resolve for its speed.
Apple used to have a much larger selection of creative software like aperture. But much of those are depreciated
2)Audio production. I am completely unfamiliar with that sort of work but from what I hear macOS offers a latency advantage compared to windows but software ability is getting better on Windows. Linux has a low latency kernel option as well but not sure about software.
3) Developers. Not sure why alot of people are supprised to hear that I use Linux while not being a developer. From the few developers I know, most of them if they are on a mac spin up a Linux distro probably Ubuntu to do their work. Only a few will install Linux directly on their machine.
4)hipsters. Back in the Mac Vs pc days,apple got quite a cult following who believe that Macs are superior due to the ease of use, lack of virus etc. The original Mac enthusiast probably didn't like it's new unsavvy userbase. These days quite alot of those people migrated to iPads and ms surface tablets as per my survey of Starbucks tells me
Probably still got quite alot of niche users I missed out. Feel free to add to the list