I spoke with a multi line dealer years ago. He sold many machines. He said that 90% of the machines he sells, end up in a closet. They go out a few times, dig a lot of junk, maybe a penny or two, get disappointed and quit. The dreams of finding silver, gold, jewelry & relics just don't come easily. A great example of impulse buying. Maybe 2-3% of the people actually go out and do well. Regularly getting good finds takes a bit of hard work, time and experience. Not for everyone! This conversation happened 25 years ago.
So, the tens of thousands of detectorists just doesn't happen. And......it's even harder today to get silver, gold and relics, as a lot of places have been hit hard.
All the forums, videos and other social media available paint a dream picture in peoples minds of easy wealth. In reality, it takes a lot of time, experience with detector, research, right machine, right coil, right location etc. to regularly produce good finds.
If only we just showed a pic the junk we find on each hunt, sales of machines would drop drastically!