The Tenderloin has been a slum since Dashiell Hammett lived in there in the 1920s. The reason it 's still a slum is policy. The land is obviously mega-valuable. The libs who run the city think it would be a human tragedy to eliminate the last great urban slum in the middle of any otherwise functional American city. Junkies, hookers, thieves, etc. "deserve" a nice location. So the Tenderloin will never be allowed to improve.