1. Superior performance. Native apps are just faster. They launch faster. They use an order of magnitude less memory. Multithreading via GCD is much much nicer than Web Workers. Large files are better supported. You can have very large tables. etc.
2. They properly implement Mac UI idioms. By comparison even the nicest Electron-like app (VSCode) violates many longstanding expectations: it doesn't properly highlight the menu bar when typing a key equivalent, menu items don't disable properly, the text highlight color is wrong, text selection anchors incorrectly, no column selection, text drag and drop is badly broken, undo doesn't know what it's undoing, undo coalesces incorrectly, hell even arrow keys sometimes go the wrong way. It's an island app doing its own thing.
The theory of the Mac is to establish a set of UI conventions. When you launched a new app, you would already know how to use most of it, because it was a Mac app. It looks and behaves like other apps, so you feel at home already. And as a developer, you get the right behavior now and in the future, for free.
But if every developer builds a cross-platform app with a custom framework and appearance and behavior and UI, then the OS loses its role in defining the platform conventions. In that event, what's the point in having more than one OS?
From a developer point of view, it's just better to make a Web App or a Electron App that will be used by everyone irregardless of their OS. Not only it's less of a hassle to develop but also guarantees that more people are gonna use it.
I'd also argue that VS Code isn't much worse off than most native code editors. Most code editors outside of Xcode don't use NSTextView and so have to implement all of the behavior themselves anyhow. For example, as far as I'm aware Sublime Text pretty much implements just as much of the core editing logic as VS Code does.
I'm not denying your complaints, of course--they're valid--but I don't think the gap between native and Web/Electron is as big as you're implying.
Whereas developing Mac apps seems to rely on a set of arcane knowledge and having been in the scene for years. The documentation for AppKit is vastly outdated and there is almost no blogging/tutorials scene so as a newbie you are basically going to be going through a lot of trial and error.
And then most of the documentation you will find is in ObjC while everyone around you is telling you to develop in Swift, but then Swift changes every few months. You open up a project from a few months ago, it doesn't compile anymore, and you basically have to work at Apple or be a dev god to fix it.
So.... native is easier to develop for? No way.