Restriction of things creates a market for it. Why do people buy ivory elephant tusk, have exotic pets, or buy fully automatic guns when they are hard to get or illegal? It's the desire to get something that others don't have, regardless of how useful or playable it is. The cards aren't banned in kitchen table magic, which is what WoTC wants us to believe is the one of the biggest formats in magic.
They will have a demand because these cards make people uncomfortable, are harder to find than other RL cards, and are the first cards in MTG to have been banned (HUGE historic banning that we've had in the entire game of magic)from all formats due to artistic direction or name. Most of the cards aren't that great, but they are unique in those regards.