Most people don't use their yard. They don't have more than a few flowers in the garden. 20 minutes with a push mower is enjoyable exercise but they wouldn't want it to take longer.
My big problem with cities is the people.
If these buildings were properly soundproofed, in many ways I'd prefer living in the city, but as things stand the only people who get to enjoy that in cities are those at the tops of skyscrapers renting penthouse suites, all of whom reside in a plane of existence entirely separate from my own.
The number one thing I've enjoyed about suburb life, particularly as a remote worker, is how much more dramatically quiet it is, primarily thanks to not sharing a wall with anybody.
I do enjoy walking on the grass and taking care of some plants, but I didn't really need so much land if not to keep neighbours away (I used to live in an apartment where a neighbour made my life hell, never again).
My family member just bought a ridiculous gas-guzzler to drive even more ridiculous distance to their job and still manage to muster up courage to complain about gas prices to me. It is not the use ( or lack thereof ). It is the lack basic sense.
I don't have a mega yard, because I can't afford the upkeep. If I could, I would consider it.
In the case of your family member sure they lack sense, but I've found for lawns at least, to lean into that and use arguments like, 'hey clovers are better because you don't need to mow and barely need to water, this means you can sit on your ass more!' (something like that).
Understand that most people over manage their lawns. You can get your lawn a little more green (the color, not the environmental green) with excess water and chemicals. They are not needed at all though.