One of the reasons I left Washington State for rural KY was the rainwater thing. It was the principle. I felt like I lived in the old USSR in many ways. That was one of them.
There are few events more unsettling than a toilet not refilling after flushing ... and no expectation that it will for some time. One of this summer’s projects is to set up real rainwater collection (built makeshift last fall when Hurricane Irma was targeting us).