However, I'm not really sure that this is the kind of knowledge that you talked about. I mean it certainly doesn't hurt to know of this, but I don't really think this is what is meant when we talk about American's financial illiteracy levels.
There are countless reddit posts where people don't know that tax refunds (except in the case of certain refundable credits) simply repay them for taxes they already paid in but did not owe that year. People who don't know what the difference between the minimum payment and the payment needed to avoid interest is. People who routinely use overdrafts as a form of credit. People who use high-fee prepaid cards to "avoid overdrafts" instead of simply not making them.
And as smt88 said, there's just not much profit in that. There are perfectly good websites, blog posts, and videos out there that cover this already, and it can't really be coupled with data for monetization the way stocks can. Frankly, while it absolutely should be taught to kids, there's a point at which if you're an adult and you can't sit down for five minutes to read an article about how your credit card works, its no one's fault but yours. I agree that optimizing for readability is great, but I don't know that "no one will read black text on a white page." That describes a book, after all.