Yeah, it's dumb: people on cisterns will be far more conscious of their consumption (and possible reuses) than someone on a well or municipal connection. And hauled water will have better quality assurance than what comes out of a well.
But I have similar experience at a cabin without winterized plumbing and an iffy cistern, so over winter we haul in water too and melt more as needed. Probably going to install an incinerating toilet to augment the privy one day. It really makes you think about need vs. want. Lots of great USB-rechargeable pumps for hand-washing and shower head doo-hickeys these days.