I NEVER paid attention to the Top 40.
My music life started with The Beatles in1964. And yes, they were played a lot on the radio. But why even bother with that, when you could play Beatles albums full of songs, instead of waiting for the radio to play them. Meaning that, when The Beatles came out in 1964... that's ALL I wanted to listen to, day and night.
As a teen, all I was interested in was album rock, and I had not desire to know what the latest song was at the top of the teeny-bop charts.
Admittedly, in the 1980's, I listened to what would have been on the Top 40, but that was by way of MTV, with New Wave music, and that was not based on anything the radio was or was not playing at the time.