So those places you describe probably operate just like regions along the USA-Canada border that accepts both currencies and do conversions on the spot based on the currency trading values for the day.
You are 100% incorrect. Please see the list of countries which have adopted BTC as native currency, and the residents are using Bitcoin over LN for retail transactions. I have a Lightning wallet on my phone and use it for retail transactions…no different buying a pint with BTC than tapping a credit card.