Earlier quoted context omitted.
Probably not. I'd prefer the mileage, peace of mind that I have recourse, consolidated statementing, free 30 day loan, etc. And you would not save 3%. In fact, with Bitcoin's volatility, you might be charged 3% as you are now when you purchase in a different currency. Bitcoin enthusiasts have a difficult time understanding the cost of currency volatility.
And yet, it's pretty common to pay with cash at any brick and mortar store, where you have no electronic protection (like chargebacks) and not even any physical protection for the cash you carry around.
You're correct that there is no physical protection for the cash, but that is why most people do not carry lots of cash. Most store it in an insured bank account.