I live/work near two small towns with efforts to "revitalize" their small downtowns. They're doing a lot of the right things to attract young professionals, but both of them are investing in small 1-, maybe 2-bedroom apartments and not apartments large enough for families.

If the numbers are similar even for larger cities then I'm not surprised why people move out to the burbs - a 1 bedroom apartment gets very cramped with kids - especially when you don't live somewhere like NYC/SF with enough parks/amenities around.