It is a niche feature, but it is still used eg when an application wants to have good control over a screen's frame buffer to display sth in an external monitor and minimise disturbances. I think it is fairly standard in psychophysics experiments, at least with some software. That's where I worked with such a ("zaphodsheads") setup.

They are also roughly analogous to the modern DE concept of "Workspaces" which people seem to enjoy.