You said it yourself, it would be hard to fill a queue simply because it's being *TOO* specialized. It'd be something exclusive to those who spent the Zen to buy those ships in the first place.
"My frozen dairy-based confectionery attracts all the males of the species to the facilities. They all agree on it's superiority. Indeed, it is superior to yours. I could teach you the finer details but that would require monetary recompense on your part." -The Milkshake Song: Vulcan Edition