I've never understood it either, i.e. renting a water heater. Really? Does one rent their furnace? their kitchen appliances?
Mind you, I've also been bewildered about calling electricity "hydro". Does it look like water? Okay, I get that Adam Beck started the ball rolling (in a significant way) with hydro-electric electricity but seriously WTF is hydro? BC is almost entirely hydro-electricity with most of it delivered by BC Hydro but no one I know here calls those electrons hydro.
OTOH, maybe milk in bags is more manageable. Buy a Rubbermaid pitcher and that may be more convenient than a recyclable plastic (or waxed) carton. Y'all do strange stuff 'down east'.