I'd argue that the desire to have windows side-by-side when multitasking is far more common than to have them be particularly overlapping and hiding one another. Certainly a lot of what I do on a computer is development, but tiling makes composing emails, image editting, writing, and web browsing less painful too. Floating windows seem to be prioritizing a metaphor over usability.
The widespread shortcut/gesture for making a window full height and half-screen width was a good middle ground for me.
Tiling WMs (which I tried 10 years ago?) would always break on some programs (say Gimp), then you had to run that program in "floating mode" and its already too much overhead for me...
