High resolution displays for example impose an exponential cost right out of the gate. Just printing "hello world" requires more pixels as a function of the square of the increase in resolution. That's more memory, more memory bus traffic, larger bitmaps, scalable vector graphics formats that take more processing power to draw, antialiasing, ...
Again I am not writing off bloat. We could probably shrink most software by at least 2X and most Electron stuff by 3-4X. I doubt we could shrink it 10-100X though without sacrificing some of the things I listed up there, especially all the eye candy and rich interaction media.