If there were an evolutionary advantage for more things to being in an arid region over being in a place with abundant, easily accessible water, I reckon the niche would have been filled. the natural world isn't really "interested", for lack of a better term, in maximal efficiency outside the context of following the path of least resistance in any given domain. Lightning might strike your chimney even tho there's a giant metal tower 300 feet in the air a quarter mile down the road that appears to be a much better path to ground.