Consider: Back in the 1950s and ’60s, people thought it was normal for a family to have one bathroom, or for two or three growing boys to share a bedroom. Well-off people summered in tiny beach cottages on Cape Cod or off the coast of California. Now, many of those cottages have been replaced with bigger houses. Six-room apartments in cities like New York or Chicago have been combined, because upper-middle-class people now think a six-room apartment is too small. Is it wealth? Is it greed? Or are there more subtle things going on?
This is extreme wealth. It is also part of the reason housing prices take an ever increasing multiple of median income. Basically people are buying two houses (not just one). Average square footage of single-family homes in the USA: 1950 – 983; 1970 – 1,500; 1990 – 2,080; 2004 – 2,349.