Some people don't have the means to make an informed vote, mate. When you live near the poverty line and there's no heat in your rented apartment and you are waiting on your paycheck to buy gas for your car and some cheap groceries to stay alive, you don't have the leisure time or energy to go mail in a ballot or stand in a line. And, in the end, they are an insignificant vote, as the majority will likely choose the predetermined and preferred candidate or just vote for their own party. They may as well use the time they would spend waiting in line and filling the ballot out to pick up some overtime at work.

It's like the deal with the ancient Greeks-- mostly only the nobles made significant contributions to the arts and sciences, not necessarily because the poor and the normal folks couldn't or didn't understand those things, but because they didn't have the time, energy, and money to pursue those things.