You're getting your money back and a bit of everyone else's who has to use cash. Visa is splitting the ill-gotten gains from its market power with you so that you'll help keep the system going. It's mildly unethical to use credit over debit. That 3% skim isn't from doing something socially positive, it's completely zero-sum.

Let's unpack what you're stating, I think you have misunderstood something:

Retailers often include their half of CC fees in the price you pay at the till, regardless of whether a cc is used. This is on top of any fees you may pay.

Since it's the retailer deciding to leave their CC fees in the retail price, I'm getting back my money on my purchase.

It's the retailer who's keeping the extra few percent on their prices, not visa, or you, when someone is paying cash.

The questions of ethics is interesting. While I appreciate the morality checks from strangers at any time, if the retailers are pocketing the extra %, instead of providing a cash/debit price, should disdain towards 'ill-gotten gains' be focused on each 'mildly unethical' retailer you are dealing with?

Are you suggesting that you use a credit card to combat credit card fees?

That feels like "not solving the problem"

Actually it feels like the prisoners dilemma: if everyone chooses what's best for themselves the we're worse off overall...

Not suggesting a solution at all. Just was curious if the original poster was aware most thing we pay for in cash are inflated to include the retailer's credit card fees.

What might be interesteing is a till discount at each retailer for not using a credit card.

I preferred to use debit for a long time too. As fraud increases, I'd rather the bank be hit with fraud on a CC instead of my bank account. It's not the best insurance, but banks are far more motivated to get their own money back quickly over their customers'.

That ship sailed long ago, though, and nothing short of the collapse of our financial system will bring that ship back to dock. The only rational decision is to "defect" in this particular dilemma: cooperating just hurts you and doesn't change the overall outcome for anyone else.