Why is it that the rich get richer and the poor stay poor?

According to what I learned in Geography class, just 1% rich people owns more than 33% of wealth in US. It means that the gap between the rich and the poor is already too large to overcome in short time. Therefore, the rich gets richer while the poor stays poor. For example, an owner of a company is going to hire foreign workers due to their lower salary. At the same time, local people do not have enough job opportunities and look for the jobs with lower income. It implies that local and foreign workers will have lower income while the company owner can make more profits by spending less money on workforce.