I totally understand this in southwest states like Arizona and New Mexico, where water conservation is really important. But the bulk of the country essentially has infinite, cheap water. It doesn't make sense to me why you would need this in Iowa.
Many cities in the US are having serious issues with their sewer infrastructure, so even if they have copious fresh water, dealing with it after use is an issue. Here in Portland, where we have no shortage of water, I still pay more for my water than for any other utility, mostly to fund upgrades to the sewers.
Even where you have a lot of cheap water, sewage still has to be proccessed.
What happens to the cardriges?
When people want to save water they think... I'll use water-less toilets! Now they have two problems.