They are selling Monero coins below real market price (Market price is not what HTX shows -you can't even withdraw 100 XMR from there), that's why they are still empty. Supply and demand. You can talk about it as you like.
For example, on March 15th they sold 20k in one day for $220 a piece without KYC, where else would you buy it so cheaply, quickly and with these conditions?