Well, thanks for asking this, it turns out to be a fascinating story. It seems that the rich own and regulate the means of becoming rich. And they have done so for about 10,000 - 12,000 years or so.
About 600 years or so ago, the rich decided that it was important for the poor to have to work very hard indeed for a subsistence living and that they have little if any leisure time.https://web.archive.org/web/20170108123038/http://www.pieria.co.uk/articles/mercantilism_six_centuries_of_vilifying_the_poor
Because the rich own the means of getting rich, very few new people can break into richness without the prior approval of the rich and they tend to reserve richness for family and friends.
For example, during a short period in the late 20th Century, software development emerged as a path to new richness, but now the rich buy out newcomers well before they get rich. The path that made Elon Musk rich is now more or less closed now. The rich are busy closing loopholes that allow non-rich to become rich and opening loopholes to allow the rich to stay rich.
The poor can work as hard as they like, or as hard as the rich force them to work, and they will never be rich. Because not only do the rich own the means of getting rich, it turns out that they also own the products of the labour of the poor. The poor never get to keep the products of their labour. They have to give all of it to the rich, who then return as little as they can get away with, often considerably less than it takes to stay alive.
Even a small business person is extremely unlikely to become rich—most self-employed people are either already bankrupt or well on their way to becoming bankrupt. They are crushed by the rich.
In the middle, but much closer to the poor than the rich, we have the people who oversee the day to day business of ensuring that the poor remain poor. The poor can aspire to be overseers, but competition is fierce to be an overseer, and mostly the poor don’t get access to the education needed for that, and the educational requirements only go up over time.
The coup de grace is that, nowadays, the rich have convinced the poor that this is the best of all possible worlds. The poor are convinced that if they were in charge it would be chaos, mayhem, disaster, catastrophe, madness. So they conscientiously vote for the rich to be in control.