Yeah, I know for me, to turn off the power at the box downstairs before this, but the next person might not. I did throw a label on the cap/tape saying unused.
I was going to disconnect it from the plate on the wall, but had not, as of yet. I'll do that.
If/when we sell, I'll replace the box on the wall so there is only two switches instead of 3 and just leave the unused/capped third wire there for the next person.