This rings true to me as well, but why is this the case? If we roughly assume that Mac users are 1 order of magnitude fewer than Windows users, they must be >1 OOM more likely to pay for these kinds of apps to generate this impression.
I struggled with this puzzle for quite a while when I switched from Mac to Windows. Utilities are simply not comparable, either in design, functionality, or simple quantity, for a market which is (on paper) both much larger and much older (if you restrict your view to the OS X era).
As an aside, it totally makes sense to me why Linux utilities are numerous and awesome, but have (usually) poor graphic design, because that Bauhaus-esque function over form describes how I prefer to work, too.
Because the Apple macOS ecosystem already has an coherent design at the point where I (as a macOS user) would hate to bring another app that breaks the coherence.
Also Apple's official apps are generally much better than the MS ones or Gnome ones (see IE vs Safari) which makes the expectation of users higher.
IMO Apple really made a great, healthy ecosystem around the macOS.
Secondly, there is a lot more money in the business and specialist app market for Windows. I worked for 3 years at a company developing a Windows application. We charged $5k a year for a license plus a good 50-500 consulting hours to adapt the application to our customers business. That was a solid business targeting a niche market, and there are countless companies like that around in the Windows space. Those opportunities don't really exist for Mac developers. Most people specializing in Windows desktop development end up working on stuff like that if they don't end up at Microsoft/Adobe/Autodesk etc.
If I was to start a company trying to develop desktop applications for Windows there is no doubt I would target business customers willing to pay $1k-10k rather than trying to sell $10-100 to consumers. If I was targeting Mac users I would probably target the $10-100 consumer space.