It's not only about threats, it's pretty convenient. I do all my dd operations, feeling confident a mistake won't wipe out my HDD. I have a work vm and a personal vm (and many more), and I can share full screen on my work vm knowing that all personal windows are hidden.
I have files and programs organized by vms. I can try installing new applications in a disposable vm knowing well that all their files will be wiped out when I close the vm.