That's it? All you have to do? Wow I'm surprised nobody has thought about that especially people who, for example:

Are born with chronic illnesses or develop other illnesses like cancer and don't have insurance to afford proper care. Thanks to the shitty healthcare system plenty of people are barely scraping together enough to afford very expensive medication

Can't avoid being a single parent because hey sometimes people fucking die and shit

Can't get a well paying full time job because they can't afford college

Have to care for an elderly relative

Have kids and can't afford daycare

Or a million other thing. Life isn't black and white, you don't just get a well paying job and everything is peachy. Shit happens, things you can't anticipate. Not to mention how difficult social mobility is in the US. People are born into poverty don't know any different and will likely never rise out of it