A little birdy told me
...that at least some classified military environments in the States use non-persistent (stateless?) virtual desktops.
As painful as it is to mention given the poor state of development, regrettable implementation and generally disdained sponsor - ChromeOS, at least at some point aimed for a similar non-persistent OS albeit without virtualization (instead using a verified boot process).
Not sure about the rest of the world, but I have always been a big fan of this approach - however it is accomplished.