Because Leftist politicians don't WANT success and economic freedom. Instead, they WANT economic and social dependence on the government, which gets to decide what you eat, what you make in the way of dollars and employment, your health care...all of it determined by politicians who the cities---and ultimately American voters nationally---continue to vote for in the fear that the hand that feeds them will also take away. It's all exposed here at Forbes, where the author explains that the "Curley Effect" has been in effect in the poorest cities in America and Leftists are hard at work trying to impose it nationally:
The Curley effect is extensive. Perhaps you have seen the chain e-mail listing the ten poorest U.S. cities with a population of at least 250,000: Detroit, Buffalo, Cincinnati, Cleveland, Miami, St. Louis, El Paso, Milwaukee, Philadelphia, and Newark. Besides all having poverty rates between 24 percent and 32 percent, these cities share a common political factor: Only two have had a Republican mayor since 1961, and those two (Cincinnati and Cleveland) haven’t had one since the 1980s. Democratic mayors have had a lock on City Hall despite these once-great and prosperous cities stagnating on their watch. This is the Curley effect in action.