This is one of those cases where we fly by and don't think much about it because we live in a plentiful environment. The more detailed we get, the more we realize that everything has a cost, and wasting water is not free as in beer. Have we also considered the disposal costs of wastewater?
I used to live in a place where water was infinite. Fast forward 20 years, now it's not anymore, the fish bearing watersheds ultimately bear the price, but everyone is still unmetered and there isn't low flow anything. If you piss away precious resources for no good reason and claim it's not wasteful, shame on you.
Yes, I have considered the disposal costs of wastewater! Yes, I still think importing hundreds of stainless steel widgets from China and then having a plumber spend who knows how many hours installing them is almost certainly a net negative. If you piss away precious resources doing that then shame on you.
Saying that saving water is "about respect" or something is idiotic. Saving water is about ensuring there's enough water to go around. This is something you need to do in places where water is scarce and not where it isn't. And if you waste time and energy on saving water you are ultimately making the world poorer.
Obviously I'm simplifying things by talking in absolutes here, but what I said above about "the margin at which it makes sense" gets at the truth of the matter. Installing water-saving taps in Zürich is almost certainly a net harm to the environment.