Do they have to join immediately? Of course not, I can understand why Thavnair, and Eulmore wouldn't immediately join.

Idyllshire however grew with time, and makes sense to have a market from the finalization of the city state.

The issues that plague the source after Endwalker are over. It's time for Thavnair to restore its market. It also has a location that leads to inaccessible housing. It's not much different in that regard from Solution 9.

Eulmore has a long road ahead of it, but a market would make sense post Shadowbringers.

Mor Dohna is littered with markets. A market board would make sense, although it is not a separate instance.

Rhalgrs Reach is debatable.

Doma has an enclave, and a desire to be on par with Kugane again. Give it a market board.

It is time to bring these end game hubs into the fold.