Why is it that the rich get richer and the poor stay poor?
"The richer get richer and the poor stay poor" is a catchphrase that is used when describing economic inequality. It's commonly used when describing the criticisms of a free market system, a.k.a capitalism implying that it's inescapable from Karl Marx's idea of the "The Law of Increasing Poverty". 

Economic disparities date back to the colonial era. By the 1600's, almost all the continents were connected together by European brutal domination which was diffusing progressively across Africa and Asia. The construction of this global colonial system started when conquistadors stole religious artefacts, riches, and land from the Incas and ruled the land as their own. This is the process of where the upper class receives communal land from the lower class families which has a result in depriving the latter from their livelihood. 

In the present day, trade policies also create income disparities, this is because economic practices such as free trade can be looked at a negative impact on a certain country. Free trade allows corporations to trade without barriers which enables them to share the income among working families unequally. This causes the rich to get richer, and the poor to stay poor.