Bitcoins were supposed to remove the bank / middleman from the picture and hence cut down on transaction fees.
If that is not happening, I don't see why you should use a bitcoin debit card. You might as well use a fiat debit card.
I think people still need bitcoin cards because in some countries the fiat debit cards has very bad limits and restrictions so they will use btc debit cards as an alternative.
I agree with you that bitcoin is created to remove those third parties in our transactions but this it not going to happen before a widespread btc adoption