You bring up a good point, we are buying more... however, it's hard to buy less when lesser houses are not being built. To get that level of "lesser" housing requires one to buy the land and drop down a modular, or just about that path, and deal with all the issues of building to taste. All the power to someone who wants to do that, and build to their desire/need, we could use cheaper housing in this country.
Two bedroom house? Was that a real thing in the past? Most families through the years had multiple kids, which means decent odds of having both sexes, and a real need for having 3 bedrooms. In retirement 2 bedrooms is fine, but for the family man (or aspiring family couple), 3 seems like a better number. [And in full disclosure, my first home was 2 bedroom that I bought--geez, has it been that long?--20 years ago, and I regret going that small now. For various reasons I took a bath on selling. Its only positive was that it was cheap and I was able to weather the financial crisis because it was cheap and didn't constrain my budget.]