Earlier quoted context omitted.
People get much larger houses today because they can afford much larger houses. This comes from both increased prosperity and having fewer kids. 1950s: The average new home sold for $82,098. It had 983 square feet of floor space and a household size of 3.37 people, or 292 square feet per person. 2010s: The average new home ($292,700) offers 924 square feet per person (2.59 people per household, 2,392 total square fee…
Around here, they're building bigger houses, but also on much smaller plots without gardens or dogs or tree-houses or places for kids to play outdoors. I suspect it's the same in a lot of places. Maybe these square-foot-per-person calculations should also include square feet of land.
All these are places children used to go unsupervised, but now mostly don't.