I have two university degrees. My daughter has three. My youngest has only a few more classes to graduate, and my middle kid has two years to go, but has been on the dean’s list more than once, so I can tell you why people don’t finish college: Lack of attendance, incomplete, late or no assignments finished, on cellphone during lectures, lack of participation, studying for finals at last moment and lack of motivation.
It has nothing to do with which high school you attended or your income. Do the work and you get the degree. It’s that simple.