Following my
intensive research into this group of fishes I suspect that they are very delicate in physiology and die quickly after being netted? The stronger individuals likely perish in holding tanks from starvation when their nightly feasting of planktonic items isn't found in the filtered captive waters of the wholesalers.
They are also easy to eat and likely more valuable as a pizza topping in places where they are captured than being wasted in captivity to die before they can be transported to the LFS's around the world.
Not to mention that the pictures and descriptions talk about grey, brown, dull colors and small fishes that are not going to excite many hobbists besides the OP to purchase one if it appears as an odditty in the fish trade.
I have a soft spot for the lamphreys and hagfishes and they are also not popular in the hobby?