A diamond is a lump of carbon, and it doesn't care about your nuptials. All the different brands of vodka taste pretty much the same. Before Marlboro was a brand so butch it routinely killed cowboys, it was a ladies' cigarette with a red band to hide lipstick marks. Advertisers would rather you not dwell on these facts--but facts they are, as Katie Connolly points out in a BBC story about how marketing campaigns have shaped our perceptions.
"Prior to the 'A Diamond is Forever' campaign--which launched in 1948 and was named by Advertising Age as the most effective campaign of the 20th Century--diamond rings weren't synonymous with marriage or engagement," Connolly writes. "Peruse 19th Century literature and there's nary a mention of diamond engagement rings. But DeBeers changed that. Diamonds aren't particularly rare, but they are the hardest substance on earth--a quality that lends itself to notions of eternity. In pointing that out, and infusing it with notions of romance, DeBeers literally changed Western culture."
Connolly goes on to cite, among other triumphs of advertising, Absolut's achievement of making people believe there are important distinctions between different kinds of vodka; Nike's co-option of the very idea of physical endurance; and Lyndon Johnson's successful leveraging of nuclear hysteria over Barry Goldwater, a noted pro-dropping-atom-bombs-onto-children candidate--see the BBC story to get that one.
(For those looking to learn more about the arc of diamond marketing, this 1982 story from The Atlantic is worth a read. Meanwhile, here's the Mad Men reference that journalists are now required by law to insert into any and every article about the advertising industry.)