> Look at movies set during various decades;

In the 90s a lot of movies had accompanying songs that would go into the charts. I remember Titanic, Bond movies, Godzilla, gangsters paradise, some Bryan Adam’s and Aerosmith songs.

I don’t know if that is still the case today as I listen mostly listen my own Spotify playlists or ”classic” radio stations (meaning 90s/00s music nowadays).

I can imagine it was an effect of the commercial music industry at the time and these songs were heavily subsidized by the movie’s marketing budget to get into the charts.