Although I will admit that having a water maker is a really nice convenience, the judicious use of onboard water can be easily learned. Like fuel & battery capacity, fresh water on a boat is a management problem. When I went to Catalina Island last April, I had four adults on the boat for 4 days & 150 gallons of water. That works out to 9.73 gals/person/day. (Drinking, showering, etc.) I published this factoid in a "Welcome Aboard" letter to my cruising friends, along with instructions on using the head, emergency procedures, etc. We also had 54 small bottles of drinking water & plenty of beer & cocktail supplies which we didn't manage as well as our water supply. When we returned to San Diego, we still had 60 gallons of water in the tank. (Note: Everyone used the shower but did it in a marine fashion. (Get wet, turn water off, soap down, rinse off. ) This resulted in a lot of laughs but no one was put out!
I will admit that cruising for days & weeks at a time, having a water maker would be a necessity but for most of us, managing the onboard supply, judiciously, can go a long way!