Another "multi-user" use case on my "single-user" laptop is having a separate account for downloaded software (government contracts sometimes require such things), for which I don't want to take the risk of polluting the rest of my system. I install in wine in this separate account, and share (minimal) data as necessary. Security matters.
[OT: it's astounding to me how well wine runs a *lot* of Windoze software these days!!]