Fury Mounts over a Global A.I. Frenzy

Main "issue" is that evaporative cooling is just ridiculously effective compared to a normal heat exchanger with only air.

You can use water or air internally but then to get rid of the heat from the facility there aren't many choices. You either put it into the air which is cheap, into nearby water bodies which has other environmental concerns, or into the ground which is expensive. The air is the simplest, cheapest solution and using water for evaporative cooling in dryer climates makes it even better