> Shouldn't the “credit score” prevent Americans from going deeper and deeper into personal debt?

The credit score is often used as a indicator of financial risk as @RonJohn stated.

Here is where it gets perverted in US Financial... Banks know low income folks and others with low credit scores are riskier, so they still make the loans but at a higher rate. They make lots of money on the high interest loans. When the loan goes bad they sell the debt to a collector and still make money.

US Banks recognize how lucrative a market it is to lend to low income/high risk customers. In fact some banks, like Capitol One and Bank of America, specifically targeted low income/high risk folks because it reaps so much profit even with the loans going bad.

I believe Bank of America boasted 30% of their profits came from the lowest 20%-income folks (the poor people, not the rich people). I don't know if that continues as of 2019.

In the US this is one of the practices known as a ["ghetto tax"](https://en.wikipedia.org/wiki/Ghetto_tax). US law does not forbid the predatory behavior.

(I've got a PBS documentary on DVD that discussed this. I'll try to find it for a proper reference).