That's what Cornelia asked me on the phone when she got home one day.
I had left the house with headphones on, so I didn't hear that I had left the water running in the kitchen.
Luckily (?), we pay a flat rate for water as we have no meter, so my mistake -- leaving the tap open for 2 hrs and thus wasting about 0.73 m3 of water ( 120*6liters/min = 720 liters) -- cost nothing. Had we paid the price of metered water (about €1.50/m^3), it would have cost about €1-2, but it would have FELT far more painful (like dropping a coin in the canal).
Anyway, the point of this post is that meters make people think different about water consumption, but so do some other things. I got a plumber to repair a leaking toilet last year (cost about €100) because we were renting out to Airbnb people and a leaking toilet is annoying. The cost was far greater than the water lost (ignoring that I don't pay for that), but it's been nice to have a quiet toilet :)
Bottom Line: Nobody wants to "waste" water, but meters (price incentives) will encourage them to take actions to waste less.