So I'm not really sure what your standing point is anymore. You yourself admit [0] that children and adults don't have the same contractual capability. Your example relies on a ridiculous presumption which exactly proves why minors are not considered capable. And now you're on to people regretting financial decisions, to which my response is, who doesn't?

The information is there, if they do the math. Failure to crunch the numbers is, in my opinion and in the law's, not an excuse to void a contract. Changes like credit card statements showing the results of paying only the minimum payment only do the math for you, not relay novel information. They are only valuable in the sense that people can no longer not do the math and remain ignorant, because it is already done for them.

[0] https://news.ycombinator.com/item?id=11060258