I learned an important lesson about this in my very early twenties when I applied for a summer internship at a local firm. There were only two interviews: one with engineering and one with the owner. The owner gave me the internship on the spot not because of my qualifications, but because he liked the way I dressed and spoke. His words to me were something along the lines of "I feel comfortable putting you in front of our clients."
One of the reasons poverty is so disabling is because it changes the way a lot of people ( but not all people ) carry themselves. People from wealthier backgrounds often present better and get first crack at opportunities as a result. Note that when I say "present", I am talking about mostly superficial qualities, not level of education, skill, or other deeper qualities.
Anyone can learn to present themselves the right way, with respect to speaking, dressing, and credentials - although it's extra work and extra cost for those who have already fought very hard for their chance to climb the ladder.