Because they think they deserve it. "Oh, he deserves to be poor, its their fault". This along with the hope of poor people to get rich, constitute the fundamental pillar to keep the capitalism scam going.
Because many times it's true. Having been on both sides of the fence, people with money either inherited it or worked hard for it. In the case of inheritance you can't do much about it, but you can be damn sure their parents/grandparents worked hard for it.
Working hard doesn't mean getting up early every morning and going to a 9-5 job that pays $4 an hour. It means understanding enough about the world around you
and yourself to manipulate it into making it change for you. What are you good at? What are you lacking? Are people in your life successful, or do some relationships hold you back? Being around smart, successful people is inspiring. Being around laziness tends to inspire the same. Do you have an education? If not, why not? Information is free and it leads to understanding, and that can make you wealthy.
Life is hard and full of failure and pain. I was born with next to nothing, so were many of my successful friends. If you constantly complain about the rich, how "capitalism" is scam, and how their wealth should be distributed to you in some sort of socialist utopia, I have news for you. You will always be poor.