In the pre-prohibition era there in fact WAS a free lunch. It was quite common for bars/saloons (which were often owned by, or exclusively served beer by one brewery - more on this in another post) to offer free lunch to patrons with the purchase of a drink. The free lunch was often a buffet style meal with plenty of salty options, all but ensuring that the patron ordered another tasty beverage. These "loss-leaders"of the time were thought to be effective at bringing people in for lunch and also for creating loyal patrons.
In fact, during the temperance movement, the free lunch was one of their major complaints. Too many husbands were coming home after work intoxicated. This passage below is from an 1874 document distributed by the temperance movement.
"In the cities, there are prominent rooms on fashionable streets that hold out the sign "Free Lunch." Does it mean that some [philanthropist]... has gone systematically to work setting out tables... placing about them a score of the most beautiful and winning young ladies... hiring a band of music? Ah, no!... there are men who do all this in order to hide the main feature of their peculiar institution. Out of sight is a well-filled bar, which is the centre about which all these other things are made to revolve."
I have to say, I'd personally welcome a free lunch with the purchase of a pint...