Water usage is probably my biggest. Living in a high desert, my wife and MIL see no problem with filling one side of the sink with hot soapy water to wash a few dishes because “that’s just how I’ve always done it”, to watering the grass and plants for hours. All of this makes me mental.
“The Puppet Masters” by Robert A. Heinlein. There’s an acceptable movie version of the book. The marriage scene isn’t in the movie, though.