Pruitt-Igoe was part of a response to the mass homogenization of St. Louis. The response to this widespread and aggressive degradation ('slumification') was a similar the homogenization of lower class housing and an inverse condensation into housing blocs consisting of homogenous, bare-bones units and landscapes.
The embodied experience here is comfort without excess. For the residents, it was the pursuit of the American dream. This isn't the contemporary American dream, of making it big with a minimum of effort; it's an older, more modest one, the American dream of Horatio Alger: of achieving success through hard work, and receiving a commensurate and relatively modest reward.
The initial degradation of St. Louis is a result of this--people fled the city for the suburbs, an ideal realm of comfortable homes with well-kept lawns behind the archetypal white picket fences. Pruitt-Igoe was an attempt to urbanize the dream.