I’d assume it’s cheaper to fuck up the environment.

It’s as the case is with everything for these parasites: if it loses them too much money or makes them too little, they avoid it like the plague. It’s cheaper upfront to just run it through an open system.

Because it's considerably cheaper to do it this way and they're being allowed to do so. Why would they spend money building giant cooling towers when they can just dump the hot water into the river and then drain main supply for fresh supply.

They usually do. They just do the same thing a lot of nuclear reactors do and also evaporatively cool one end of the heat exchange loop.