Why would lightning layer not be for the average Joe? It could be literally without fees if he and Starbucks agree there should be no fees. What would be the incentive for any of sides, he and Starbucks, not to do it?
It is certainly possible and might even happen for a while but you don't need the worlds most secure network to secure coffee funds. Opening a lightning channel could still cost Starbucks or the customer $10-$100 in fees to open or close on the bitcoin network. More likely Starbucks would open a channel with your bank and it's suppliers and close the channel each day, week, month to settle the account.