This is a nice thought, but come on. If you want to be a good samaritan, donate to a charity. Giving up 2-3% cash back by using cash while plaintively reminding everyone that interchange fees are harmful to society isn't making any difference to anything other than your own wallet.

Also, some cards automatically apply rewards points. My Schwab Amex card deposits my 2% cash back each month directly into my brokerage account. My Amazon Prime card just gives you a checkbox when buying on Amazon where you can apply cash back to your purchase during checkout.