When I first saw performers with ear monitors, I assumed that they were hearing aids. I knew that performers in rock groups often went mostly deaf after fifteen or twenty years of sound set too loud, and I figured the loud sound at Southern Gospel concerts was catching up with the performers at last. Of course, I eventually learned what an ear monitor was.
(Parenthetically, if a performer is 85% deaf, like Libbi Perry Stuffle is, I have no problem with that performer using either hearing aids or ear monitors.)
What I find particularly interesting is when a performer uses ear monitors for some songs and not others. Generally, when this happens, they use monitors for songs with a soundtrack (and, presumably, stacked vocals), and take it out for the all-acoustic piano-and-bass-guitar songs. I’ve seen groups do just that both in live performances and in videos. At least in the videos, the cut is typically arranged so that you don’t see the monitors going in and out, but you still see some songs with the monitors in the performer’s ears and some songs with the monitors hanging off to the side.
I can certainly see the usefulness of ear monitors, but they can sometimes be as distracting for the fans as they are for the artists.