To me, the most obvious explanation is that people used to be able to buy houses a lot more easily than before. My wife and I were lucky that we were able to afford one, and because of that I have my friends over a couple times a year to hang out and have dinner (I would do it more often, but we're in a remote part of the city that isn't great to drive in). When we were in an apartment, we didn't even have a dining room or enough seats for anyone other than on the couch.