[wyclif]

One reason why is because Americans are more atomised culturally than people from, say, Mexico or Guatamala. Americans believe that you should live independently after you graduate from HS (or else go to college) and don't generally want to live in a home with multiple families or even the same family consisting of multiple generations under a single roof.

[eli_gottlieb]

Actually, sometimes American real-estate owners won't even rent a unit to more than N people who are not all blood relatives.