That's undoubtedly still more expensive than doing everything Electron, sure. But it's going to produce a nicer application: lower resources, faster performance, working better with platform-specific features (e.g., macOS's Services menu). Maybe that's not worth it for all applications, but if Electron-style frameworks that lock their applications to the lowest common denominators become the norm, the overall quality of software drops.
Electron provides a means to handle all of those environments with some admitted drawbacks on desktop. I'm not a proponent of Electron, just stating (IMO) the likely reason for it's adoption.
Do people not realize that you can use cross platform C++ libraries and essentially get the same program to compile on three different platforms, then just write it once? It really isn't that difficult. Use Qt, or Juce, or FLTK, the standard library and a couple of cross platform libraries for things like networking and you are in the clear.
The idea that anyone is actually maintaining three separate versions of a program is completely detached from reality.
There are good "non-native" frameworks - Qt comes to my mind first, but Flutter and the now seemingly revived WPF are also good contenders. Those are pretty great.
You can also do Electron well (VsCode), but almost no devs do it, which makes me question whether doing it well might require just as much effort as using something else.
Are there any stats that back this up? It wouldn't surprise me if it was more than 3 times the cost given you'll likely have a larger team to coordinate.
All things being equal, I'm sure companies would love to develop their apps using native tooling and have them simple, beautiful, accessible etc. Doing this 3 times for 3 times the cost, as opposed to once some sacrifices is the obvious reason for this widespread adoption.