You do have some valid points - for people who pay cash vs those who use cards AND pay off those credit cards every month.
However, for those (far too many) people who use cards but don't pay off their balances every month or within a couple/few months, the X% cash back benefit can quickly be undone/negated by the interest that accrues on the debt. For those people, perhaps using cash might be a better choice because they wouldn't incur cash-back-undoing interest and might save money because they not even make the purchase(s) due to lack of cash.
You do have some valid points - for people who pay cash vs those who use cards AND pay off those credit cards every month.
However, for those (far too many) people who use cards but don't pay off their balances every month or within a couple/few months, the X% cash back benefit can quickly be undone/negated by the interest that accrues on the debt. For those people, perhaps using cash might be a better choice because they wouldn't incur cash-back-undoing interest and might save money because they not even make the purchase(s) due to lack of cash.