I always enjoyed my business trips to NI. We’d sneak across the border into the Republic for lunch at the most remarkable pub/restaurants.
The heat was always provided by an open hearth burning hard coal and peat.
Something about the aroma and the Grant’s Gammon made the trip worth while.
My guess is, they pretty much buried everything, but finished off all the buried potent potables thousands of years ago, then couldn’t remember where the other stuff was buried.