They may have educational value. Most of the collector coins produced by the Royal Mint are produced to a superior finish compared with the normal issues. There is a demand for these superior coins. It costs time, effort and money to produce special high quality finished coins. It costs time, effort and money to produce special or new designs to appeal to the public and collectors alike.
Most people buying a collectors coin want it to be nicely packaged and presented.
This costs money. To let people know that coins are available, they need to be marketed. This costs money. The alternative is not to market coins actively, but sales of special coins would be lower, so that the increased production cost per item would increase. The Royal Mint is not responsible for secondary market prices, although if it gave more support to dealers, making photographs and other information available, this could help dealers, The Royal Mint, and its customers.