I was very skeptical when I first tried it - under instruction - but once I found it worked I just used it. It isn't necessary to believe in it, you just follow a few simple steps and it does the job for you.
All kinds of people do it; it is very common to see people in the construction and water industries dowsing for buried pipes and other services. These people don't necessarily believe in it, or understand why it works. They just do it.
I strongly dislike the implications some people make of a paranormal involvement. I think that's just hokum. I detest people who try to make money out of it, when it is a very straightforward and incredibly cheap aid to finding buried services.
As a professional engineer I think there is probably a simple explanation of how it works based on the law of physics, but the electromagnetic forces involved are probably so small that they are very difficult to measure. It is quite possible that the intrusion of measuring equipment would completely overpower or negate the small forces involved.
When you learn the technique, and it works for you, there is a real sense of wonder when the crossed rods suddenly go parallel as you walk over a buried pipeline or cable. Walk backwards and the rods cross again. Walk forward, and keep walking, and they uncross and recross. There's nothing you can do yourself to make this happen.
Something is doing it, but IMHO it almost certainly isn't paranormal. As I said, I think it's probably just some physics that is not yet fully understood.
To me, all that matters is that it works.