When more Census data is out I plan to look into this a bit more carefully, but I gather that along with the general (though now roughly halted) population decline in my urban hellhole over the past 60 years, as with the rest of the country, sq.ft./person has increased as the number of people/household has shrunk. This reduces overall population density and makes it harder to support foot traffic dependent neighborhood retail corridors. In much of South Philly in particular, buildings are only two stories high and there are almost no large apartment complexes of any kind.
