Earlier quoted context omitted.
SVG + JS is really quite good. You will need a few abstractions to work comfortably with the SVG DOM, but you can easily write these as you need them.
Sounds reasonable. Why don't people use it then? Are there any frameworks already available so one won't have to invent a GUI toolkit from scratch?
Another, I think, is that, to add scroll bars to a view, you have to write SVG scroll bars, make them respond to the mouse scroll wheel, be accessible, etc.
Even if we will get them, eventually, it won’t be “easily”.
I think it is easier to use HTML for layout, and SVG (or canvas) for those views that need it. You can do that now.