Question

what is an important reason for large pockets of urban poor?

Answer 1

Urban poor can be for a number of reason, including government and military influence as well as lack of support.

Answer 2

First of all, poor people are very rarely poor all their lives. Being poor is usually a transient state, something that many if not most people experience at some point in their lives, as a result of bad luck or bad judgment.

As to why when you are poor, you tend to live where other poor people do -- well, because usually that's somewhere undesirable, and as soon as you get some money again, you move away. So the only people left are those who haven't yet managed to get out of being poor, or who are newly arrived in the state. This is why those pockets of "urban poor" often include, for example, college students.

This said, there are certainly policies of government that can significantly increase the fraction of the population that is poor at any given time. For example, almost any form of socialist government will increase the fraction of people that are poor, and the more extreme forms -- e.g. a communist dictatorship -- can reduce nearly everybody to poverty, as for example in North Korea and Cuba. In essence, any system of government that reduces social mobility -- the ability of poor people, by hard work and cleverness, to escape poverty -- will keep people in the poor state longer, which increases the number that are poor at any given time.

The is a fact often missed in static analyses: that the number of poor is controlled by the average length of time that people spend being poor after they end up there by accident, and the systems that are the best at reducing the numbers of poor are those that shorten this time as much as possible by increasing social mobility.