The thing is, cash doesn't always hurt more for everyone. With cards, you might not feel it right then, but when the payment comes due, that's when it stings. A lot of folks forget how much they've swiped until they see the balance. So the pain is just delayed, not avoided. It's more about being aware of your spending, no matter how you pay.
My buddy Dave swears by the envelope system for this exact reason. He has a literal stack of cash envelopes labeled "groceries," "fun money," even "dog treats." Watching him pull from the "going out" envelope for a third beer is a whole show of regret.