Depends on the goals
The goal of redevelopment will be unique for each location, but a common theme is to reverse a trend toward an impoverished urban core surrounded by affluent suburbs. A small scale project that improves the quality of life in a neighborhood can contribute to that, along with eliminating subsidies for new suburban development. A problem is usually not even acknowledged to exist, though, until long after large scale projects are necessary to reverse the trend. Human nature as expressed through local politics.