> I remember reading a headline that being poor is equivalent to losing about 5 IQ points.

Poor people also spend a lot of time using cash equivalents rather than credit.

There is a big advantage to using credit. For example, I don't worry too much about fraud on my credit card as the reversibility means that the banking system is taking care of it. If a suspicious transaction hits my ATM card, the bank absolutely jumps on it since it simply doesn't match my patterns of usage.

On the other hand, if you are using your ATM card or cash transfer apps all the time, you're a ripe target for getting scammed. The protections are much weaker and the reversibility (if any) is much worse.

This doesn't even get into the fact that, as a poor person, the people you are transacting with are also stuck in the same system for various reasons of various levels of dubiousness.