1) My debit card doesn't cost me anything to use. Buying Bitcoin costs me 1% or more to get and that's if the price hasn't crashed by the time it clears Coinbase. So, accepting all that risk, paying more and maybe getting a discount, is a non-starter.
Suppose you are on vacation or are doing business internationally. How much does it cost to exchange your local currency into a foreign currency? I don't actually know the answer to that but I would imagine it is at least 1%.