Just to add: whenever you pay with a MasterCard, Visa or Amex, the receiver of the money gets charged 0.5 to 3.8% depending on the card you use, their payment provider and their size.
There is just no interest for a health insurance or electricity company to lose that kind of money just to allow you to have your glorious 0.25-1% cash back.
Also, people paying with credit cards tend to spend more, and those with cash back spend around 3-4 % more than those paying by debit. I seriously doubt that you actually save money by getting cash back because of this.