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.
I disagree. As far as i understood the Lightning protocol, although it's not easy and maybe I'm mistaken, if millions of customers open long lasting channel with Sturbucks there is no need to close all of them to bring funds back to fiat. Lighning channels can transfer the funds between each another, and in the end of the day Starbacks can transfer the funds from all daily transactions to "closing" channel (to call it that way) and confirm all of them from arbitrarily large number of customers with paying one single transaction fee for closing the "closing" channel. I believe they would gladly pay one opening/closing fee for each day, regarding the potential number of transactions.