Sometimes, you just don't need a circuit anymore. Maybe an appliance gets removed, needs change, whatever.
A commercial tenant hired me to bring his new rental space "up to code". This little lovely is but an example of what the last guy left behind.
As you can see, the plastic pipe originated where the two four-square boxes are neaxt to each other. While I haven't looked- yet- I would be surprised if the boxes are actually connected together, or the openings have the proper bushings.
And, yes, that cut-off bit of romex coming out of the pipe is quite live. The orange color also is proof that this install isn't all that old.
I did a kitchen remodel for a friend a couple of years back. They had previously had pulldown attic stairs added, which required cutting joists. On my first trip up there, I put my hands on the joists to pull myself up, switched on the pullchain light, then looked down. There was a piece of 12/2 NM cut squarely, not reinsulated, not two inches from where I had placed my hand. My tick tracer told me it was hot! I don't know what its purpose had been, but apparently it had been cut by the dimwit who installed those stairs.