My thought is that power can go out for days at a time after a big storm, so propane is mostly a backup electricity/aux heat source. Maybe they have a heat pum

My thought is that power can go out for days at a time after a big storm, so propane is mostly a backup electricity/aux heat source. Maybe they have a heat pump setup which switches to propane when it gets really cold. Wood is there, but somebody needs to feed it. And people inevitably get old or lazy about it and depend more and more on the convenient heat sources available.