Why is the Gaia Market a hidden building?

The Gaia Market building can only be seen maps like Marketplace, and is non-existent. Such a building being hidden doesn’t really make much sense since it could be used as a good asset for potential scenarios. I suppose you could technically get the building if you copy and paste part of the map if you create a Marketplace map using the map generator found in scenario editor. But even then that’s not very convenient.

Edit: I done so here. But even then, this is very inconvenient.

Idkwhy, sometimes I also find random units are missing from civs. At the very beginning, I thought your post was that making maps with gaia market to allow trade in 1v1…