one thing to remember is that 'kids' who grew up in the 70s were exposed to "Happy Days"/The Fonz, one of the biggest hits on tv,as well as "American Graffitti", etc, the soundtrack album s which topped the charts and were listened to by everybody; the same is true of films like "The Big Chill' and the resultant platinum soundtracks which were mostly 60s Motown;
as a result, in the 70s and 80s, these songs became part of the music of those generations as well, it became their 'oldies/classics, whatever you care to call them...
Happy New Year...