I would think that 3% is because there are other viable alternatives. Personally, I've paid for Pixelmator and Acorn on macOS because my needs are more about cropping, adding text, file format, levels, or color space changes--those apps seemed to pop up quickly and had features like hardware acceleration before Photoshop because they leaned on Apple's APIs. My industry is still heavily invested in Photoshop, so I'm already familiar with it and I don't have much of a need for digital painting.

For digital painting I usually suggest people check out something like Krita or Affinity (they are already aware of Photoshop). I just don't have much firsthand experience with them since I felt like my needs were met with other software.

Sidenote: After actually downloading Krita it is more Photoshop-like than expected. I'll check it out as a replacement for myself. There's also been a huge, but very rare, need for Photoshop at my job (we use Linux) which has always been a problem (usually in modifying textures where Nuke isn't a good fit). The current plan was to try and find a CS6 license and either dual-boot Windows or use WINE or to buy Elements. Gimp was always too much to ask of them. I'll see if Krita fits that need.

That’s not because you have 3% macOS downloads that you can say that everyone loses around 95% potential downloads. It may simply be because your app is not marketed towards Mac users and alternatives exists.

Krita is great (and I happen to be one of your 3%!).

Given that macOS has a reputation, deserved or not, of being the de facto OS for graphic designers, why do you think you have so relatively few Mac users?

90% Windows users is basically what you would expect based on its desktop market share. The interesting thing is having more than twice as many Linux users as Mac.

This could be one of those places where the efficient market hypothesis is wrong because of incomplete information. The reputation of macOS for graphic designers is well known, but if the result of that is that everyone makes graphics design programs for macOS and not Linux then the macOS market gets saturated with supply and each supplier has to share the market with many competitors. Meanwhile the opposite on Linux, less competition so more volume per supplier.

It implies that Linux may be a good market for graphic design software because there is currently less supply there than demand. At least until more of the suppliers figure that out and release their software for it. (But that may itself cause more graphic designers to switch to Linux, which would then still justify the porting effort even as other suppliers move there too.)

Many digital painters seem to have moved to the iPad and apps like Procreate which can be had for a few bucks. I also find eInk hardware like the Remarkable tablet and the like interesting, they run on Linux. Have you thought about a standalone tablet that runs only Krita? Even if it's only black/white, having the tools from Krita on a device like that would be killer.

That mirrors my experience with hobbyists. My wife doesn't like using a Wacom and we could never warrant a Cintiq. So she uses Procreate on a tablet. It's also kind of hard to get her to try new stuff because the little time she has to draw she wants to spend time drawing.

For people who do it for their job, they're willing to invest in the hardware and software. I can't speak directly to painting software, but in my industry people really cling to the software they know or the rest of the industry uses. It's an uphill battle even if the software is better or cheaper to get adoption.

Procreate is really nice, I have moved on from Wacom Tablet/Krita to iPad Pro/Procreate. I suggest any artist give it a try.

Well, I just added a tiny bit to that 3%...I hadn't heard of Krita before, but it looks great. Looking forward to trying it out.