I have a son in the "working poor" category. He is of well above average intelligence., but refused all offers of help getting some kind of education, was unemployed or underemployed for most of his twenties. He is working now as a meat cutter, but still barely scraping by. They live paycheck to paycheck. I see them spending on fast food and things like that, nothing horrible, but also not necessities. They spent $50 at the thrift store for stupid things they didn't need. It seems like no big deal, but those things add up, they don't have the luxury of wasting money. My husband and I have given them two cars in the last few years, the last my husband put new tires on, plus it cost us $500 to drive it to where they live. They think we are rich, so no big deal. We are comfortable, but only because we worked hard, pushed to get ahead job wise and knew the difference between needs and wants.
Meanwhile his sister studied on her own and passed the Microsoft system engineer certification. She made the most of a few lucky breaks and has a great job, and has far more saved for retirement that most people twice her age. Even with a good job that did not happen by accident. You have to budget and learn the beauty of delayed gratification.
The reasons for poverty are complicated, there are no easy answers. Some people manage to rise above their circumstances, some people can't make it with every opportunity given to them. For success you have to want it, believe you can achieve it, have the tools to get it, and work hard.