The house by then was heated. And she had multiple space heaters (its a century old, damp stone house). She was in her 80’s and didn’t care or believe that she didn’t need to keep the oven hot all the time to keep the house warm.
I’ve read that a fair bit of their current trendiness comes from a sort of fetish for the “country house” as a concept. Rural, less well off places houses tended to still have their coal or old style gas stoves. So wealthy people seeking to emulate that aesthetic either installed an AGA, or refurbished the one in the 2nd and 3rd homes that they picked up in those rural places. IIRC the AGA was always a more expensive model. Though they were still originally coal. Some googling says that gas and oil only came about in the 60’s.
There’s a similar tend among the yuppie class in the US for refurbishing old stoves. Though they tend to be slightly more modern ones with burners and what have. Some of them are more expensive than a new AGA (based on the US prices I’ve seen), but most of them are simply more expensive than a regular stove. And its sort of the same thing, you can pick up crap home and style magazines. And its all “shabby chic!” or “Country house style” with vintage stoves picked out as important.