Because none of those UI libraries use native controls. I want mac apps to look and feel like mac apps. I want native controls, native shortcuts, toolbars, built in integration with screen readers, and all the other things that the OS already provides.

Dioxus uses webviews for everything. Slint has invented their own set of UI components, so slint apps don't look and feel like anything else. As I understand it, gpui is somewhere in the middle.

If you run an app using my framework, I want it to feel like a completely native app that was made for that platform. It should look like any other swiftui, cocoa / uikit, winui, etc application. Native shortcuts. Native controls. Native look and feel. Small binary size. No electron. No webviews.

It's just not that hard to link to the system's UI libraries.