Encouraging / increasing demand for fishing

Ideas such as being able to fish COTOs (which we can assume the fish accidentally swallowed), or clues to treasure have already been discussed, so I would like to say something different:

One of the reasons I have not been fishing lately is because NPC fishmongers sell the [only] 3 types of fish that can be caught, which means that currently there is no demand for player fishermen. Anyone can just buy the fish from NPCs for a cheap price and craft the dishes. Since other craftable materials such as ore, beetle carapase, maple wood, animal hides, etc. are only available from other players or public vendors, why is this not the case with trout, salmon and bass?
And with the new food system being introduced today, I would like to see fish recipes be in the 4-6 tiers to increase demand for fish (assuming that they cannot be purchased from fishmongers at the city markets anymore).

More types of fish and recipes would be nice as well in future releases.

Thank you.
@Lord British

 

I agreed. We should fish more fishes, treasure maps, sea monsters ->krakens, ship parts, rares, COTO, recipes!