Well, I simply cannot imagine that anyone with half a brain is still listening to 121.5 on Box 2 below 10,000 feet in today's environment.
Maybe I don't even have half a brain, but despite your imagination, some of us (often IFR in Class G)
never get as high as 10,000 feet but are expected to listen out on 121.5.
Most incorrect usage we hear comes from airline pilots inadvertently using the frequency, i.e. they think they are on a different frequency, such as company ops, their handling agent at destination, or "Shanwick". No particular company seems to be the main culprit.
I don't turn it down, I flick the listen switch on the comms box to "OFF"; unlike turning down the rotary volume knob it gives a visual indication that it's been temporarily deselected.