> You are an economist, aren't you?

No. I do embedded software engineering for a living.

I use (in my view) HN appropriate levels of jargon (because lots of people here are involved with getting people to pay for some newfangled cloud thing or other, so I use their terminology).

In simple words: People pay more for the same (and spend more recklessly) when you let them pay by credit card, and this causes much more economical "damage" to poor peolpe than any "wealth transfer from card rewards".