It's easier to make money if you have money, but it's not impossible to make money if you don't. A flash of genius and/or stroke of luck can still take you from no money to some money, and if you continue applying skill and have reasonable luck (and take steps to mitigate bad luck) then it will only get easier to make more money. Then you'll also be able to set up your kids to start in a luckier position.

Rags to riches is rare.

It's a compelling origin story though. Past financial hardship can be spun as rags quite easily, so we hear the story a lot more than it "really" happens.