Of course it's less convenient for developers not to ship a rendering engine. But should developers' need always come before users' needs, especially for applications that live and run on their own PCs?
I agree that Electron is user hostile in the way it uses memory, but there's an answer in between the Electron and what Tauri is offering here.
Tauri could have a embedded engine and yet propose a better architecture and better use of memory in consequence. The best of both worlds.
In Chrome for instance, each tab is equivalent to a app, giving is a whole isolated process and yet it doesnt kill your machine even with many tabs open.