I suppose it’s a use you never realised you needed until you have it. Here are some examples off the top of my head:

• Sandwich press stays in same place, doesn’t have an on/off button. Just flick switch and no need to unplug when not in use.
• Power strip for the TV is wedged behind a credenza. Need to power cycle everything plugged into it but would need to move the whole credenza to unplug it. Flick the switch with a stick or arm and it’s done.
• Using power tools and want to be sure they definitely won’t turn on while adjusting them: flick the switch and no need to unplug.