Leftists think this is terrible, because when you voluntarily sign up for this instrument and then behave really stupidly, repeatedly over a long period with no reasoning or reflection, it's bad! We can't allow it! I can't say I agree with this worldview.
If you uncritically believe things like this, I have a bridge to sell you. You should praise me for it too, because that's the kind of thing you explicitly condone.
> Leftists think this is terrible
Nah, it says more about your worldview than it does about your favorite bogeyman, especially when you ignore the entire article and start attacking a straw man.
Yes the prices go up to subsidize the merchant fees. But they don't go up as much as I save in CC rewards, because my rewards are subsidized by people not using the card or using it poorly. I have 5% and 10% cards in certain categories and a 3% in all; abolishment of cards would never drop prices by that much.
As far as downside goes I've been paying with cc exclusively for a decade and I've never paid a cent of interest, so I'm not sure what it would be.