Why do many saltwater stores don’t have a refund policy like they do with freshwater?

I mostly believe that they have it this way since freshwater fish are normally far easier to reproduce in captivity, whereas saltwater are still mostly taken directly from the ocean (although this is improving as time goes on).

I would take a gander that it probably would have to do with the difficulty in getting and maintaining the fish. It is a pretty costly endeavor to keep up salt water fish healthy and happy.