The issue for most (well, at least those who are informed and not just bandwagoning) is that it raises the prices of utilities, in which case it doesn't really matter that it stays in the water cycle. If your local municipal water authority has to expand operations to keep up with demand, that is going to incur capital costs which will either raise rates or require tax dollars.

While this water usage might be not a big deal in places with abundant water, it could be problematic in some areas of the US.