There do seem to be people that believe they can talk to dead people. I know at least one that does.
Not everybody feels that way, but then not everybody can plumb either. If I don't know how to perform heart surgery, I don't worry about it. I do other things.
Could someone "prove" any of this to a skeptic? I don't believe you can prove anything to anyone if their mind is made up.
If someone would have asked me this when I was younger, I would have had a different perspective on it.
But consider this, most people in construction can witch for pipes and find them, and yet the oldest plumber posting here who is hj can't do it. I find that very strange too. But that fact that hj can't figure out witching doesn't mean that others can't do it.