Not sure why others would unplug their machines, but my practice (in the form of switching off the power bars, not unplugging) serves a good purpose.
For example, my bandsaw and two types of sanders in one corner are all connected to a power bar to which an overhead focus light and a shop vac are also plugged in. The shop vac and light are left in the on mode at all time, so every time, I switch on the power bar, the light comes on with the vac. I simply turn on the machine (bandsaw or sander) to do the cuts or sanding as the light and vac are already working. When the job is done, I have only two devices to turn off: the power bar and the tool.
Simon