It's easy to make something multi-platform, but as many lone developers on all OS's have experienced, it quickly becomes a nightmare to maintain more than one platform.

Given the ease of macOS GUI development to begin with, there are more small-time, lone developers making full GUI apps there, versus other platforms.

Other platforms have a higher barrier of entry in that regard, so the landscape is more conducive to having already started out as a team and so developing a more significant app worthy of that kind of investment.

Not a macOS dev, just a customer. The thing I value about the platform is that there are lots of these so called "boutique" apps. Apps that do a single thing and do it extremely well, with a great, native UI, with Mac keyboard shortcuts and all the behavior you'd expect on a Mac. And since your average Mac user cares a bit more about the experience and aesthetics and is, let's face it, usually a bit more affluent than your average PC user, there has always been a market for those and it's become a bit of a self-fulfilling marketing. Mac users expect apps to be focused and good looking and Mac devs know that even smaller apps are viable on the platform if done well, so the platform is actually full of those nice little apps and people come to the Mac for the experience.

Pretty easy as in... the Electron stuff that everyone complains about?

macOS is just a joy to develop with, unix like environment, beautiful desktop, easy to use frameworks

the environment is clean and enables people to do what they want, even if XCode is a piece of garbage shit, it gets the job done

the overall quality of Apple apps encourages devs to apply the same principles, easy to use and beautifully designed apps

in comparison, when you see official Windows metro/fluent apps looking so boring, it doesn't encourage people to develop natively

then you have the details that kills it, lack of proper windows store, lack of people native way of distributing apps (exe? msi? vsx? appbundle? zip my 100's dotnet dlls?) it makes you not want to even start

even Microsoft is ditching all that crap and rewriting their native apps with electron, wich says a lot about the windows ecosystem (https://www.theverge.com/2021/1/4/22213300/microsoft-one-out...)

The macOS market is generally rich, with a tradition of niche, paid software.

One or two developers working and testing on their own machines will have an awful experience trying to make their app work multi-platform.

This type of app is going to be valued higher by Mac users.

To be fair, Windows enjoys many other little/medium/big apps that are not available on macOS.

Dev preference, time and Cocoa.

Because Mac'ers pay