Why does Philly have no pedestrian signals?

One of the first things I noticed in Philadelphia was the near complete absence of pedestrian signals. Except on Market Street, the main street in the Center City, I haven't seen any. This seems to make walking more difficult than it needs to be. A lack of pedestrian signals conveys the message that drivers are more important than pedestrians, and as a result both are often confused as to who goes first.

Is there an argument that I'm missing?  Perhaps the lack of dedicated pedestrian signals makes drivers more careful?