If it is all to chance anyway, there are probably a lot worse ways to "flip a coin". At least you can feel like you're divining where to dig.
How that ever persisted into the 20th Century and to now is perplexing but probably says a lot about human nature.
Because if it costs $1,400, and if it works then you make hundreds of millions of dollars, then even if you believe the chances of it working are close to zero it's still economically rational to try. Those kinds of returns are literally like getting a chance to go back to 2010 to buy bitcoin.
Do you hire a lottery number picker service?
You can increase your chances of finding water just by accurately reading the geology, the plant cover, the soil type, etc. Even if dowsing doesn't "work", that doesn't mean that dowsers don't have real skills that would be expensive for you to acquire.
Similarly, just because psychic powers might not be real, it would be a huge mistake to think that you're going to be able to cold read someone as well as a professional psychic.