There are so many fucking oases, it's like the land of milk and honey. Radiation and mountains mean there aren't that many walkable zones.
I had the same thought. Really, what's the point to even having an overworld map at this point? Water is intended to be a scarce resource, yet it is available around every turn. The radiation clouds can just be walked through and then you heal up after spending a few minutes running around a town or using a doctor. You can't discover towns without advancing the plot to reveal them.
So no exploration, no risk, no reward (lol caches)... what's the point?
I could see it working if the map was either 10x larger and nearly absent of oases or you could carry considerably less water. A trek out into the wastes should be an ordeal, something not taken lightly, something requiring lots of advance planning and preparation. Currently there is no reason
not to full-clear the map for all of the caches and random encounted xp/loot the second you leave Ranger Citadel for the first time, and that just doesn't make any sense.