This concept came from the "free lunch" table offered by many bars, provided one bought a drink. From an old New York Times story about the resurgence of the "free lunch":
"Before Prohibition, people were constantly trying to restrict alcohol,” said Jef Klein, author of “The History and Stories of the Best Bars of New York.” “A big complaint about bars was that guys would drink on an empty stomach. Free lunch offers popped up everywhere — you had to buy the drink to get the lunch.” Hence the phrase “No such thing as a free lunch.”
In the end, someone always pays.