It was a very popular trope in the 20th Century and up until about ...2010, when the information age took off. The 1950s and 60s had a lot of rom-coms with the much much older man and much younger woman trope. (Sabrina, Daddy Long Legs, Funny Face, Marjorie Morningstar, Sunday in New York, pretty much all of Cary Grant's later films.) And Harrison Ford was paired with Carrie Fisher in Star Wars. (32 vs. 18). Somehow it didn't bother me much in Star Wars, or all that much in Buffy (Angel 200 vs. Buffy 16/17 or Spike 190 vs. Buffy 21...) probably because both were fantasy or sci-fi?

And it's still a popular romantic trope in historical romance. Most of the romantic male leads in historical romance are about 10-20 years older than the female leads. Also still prevalent in New Adult romance.