My grandmother-in-law lived in Hawaii much of her life and now cranks up her heater in the mainland up to the 80s as well.
Did your grandmother run for President on a platform that included telling Americans they needed to turn down their thermostats to fight climate change?
My dad lived most of his adult life in the Pacific Northwest and used to keep the thermostat down on 65 when we were kids.
Now He keeps in on 80 and wears a sweater. Old people’s ability to regulate their body temp wears out like everything else.