You could be paid in BTC or Gold if most fiat disappear
The question was 'Would you spend BTC daily in brick and mortar stores", not "Would you spend BTC daily in brick and mortar stores in an alternate universe where most fiat currencies have disappeared".
and the merchants pay huge fees to use debit and credit card systems, so you pay them indirectly when you buy
But I pay the same price regardless of what payment method I use, so the rational choice is to pay by credit card, and get:
a) an interest free loan
b) increased consumer protection
c) cash back
If (in the alternate universe) paying by BTC meant paying less, it might be worth doing. But paying by cash or debit card now doesn't mean paying less, so I don't see why it would.