Why does it matter how much water a dishwater uses? The water comes from a river, goes through the water treatment plant, is piped out to homes, is piped back to the sewage treatment plant, then is returned to the river. If it's cheaper to just process more water than it is to decrease water usage, why not just go that route? This is very different from agricultural uses where much of the water evaporates or is transpired by the plants.
So, what is the problem? I don't get it.