Why can we still not see underground areas?
I believe you need to be in the underground area for that to work, it’s a function so you can see the surface area from when you are located underground, as well as when under water.
We can see different levels in cities. I think zone maps should be the same way.
I would assume it’s mostly because there isn’t much in the way of underground content. I have a feeling that if there is ever a Primordus expansion we’ll see a lot of underground territory and the underground map will appear as well.