It's a symbol of class warfare
During the Mad Men era the martini became emblematic of tax write-offs for wealthy businessmen. But there was backlash from the working class. The war against the “three-martini lunch” started with John F. Kennedy, but the first major battle was fought by George McGovern in ‘72 when he said:
“There is something fundamentally wrong with the tax system… when it allows a corporate executive to deduct his $20 martini lunch while a working man cannot deduct the price of his bologna sandwich.”
If there’s anything the 1970s were more notorious for than disco and herpes, it’s inflation. By 1976, Jimmy Carter was famously railing against the working class subsidizing the $50 martini lunch. Gerald Ford’s witty comeback -- “The three-martini lunch is the epitome of American efficiency. Where else can you get an earful, a bellyful, and a snootful at the same time?” -- might have won him the election, if he hadn’t waited until 1978 to deliver it, at a speech to the other NRA, the National Restaurant Association.