I've also don't remember seeing them in Europe when flying as a child during the 1990s. Yes, there were shared CRTs every 10-15 rows or so, but the earphones were your run-of-the-mill electric earphones, usually with a two prong connector.

I have to add these were all international flights (this was mostly pre-Schengen, and in any case I don't believe I've taken a flight between Schengen Area countries until 2023), so I'm not sure if shorter distance flights would have been different. The mid-distance flights (> 2.5 hours) I've taken would generally have in-flight entertainment if it wasn't a budget option. Some of the cheaper flights had no screens (or maybe they had ones, but didn't want to pay for the movie) and still had earphones slots connect to a set of inflight radio stations (that were also available when there was a movie being played, as an alternative).

So yes, it was an arguably "superior" experience with selectable audio, volume buttons and rather crappy drivers directly inside the earphones.