There was a time, pre-Beatles if you want something more specific, when singles ruled pop music.
Around the mid '60s things started turning toward album-length statements by artists. Of course, you could make a strong argument that Frank Sinatra was doing this during the latter half of the '50s, and you wouldn't be wrong. But generally the mass exodus toward albums didn't start until around Rubber Soul.
Still, not all genres made the move. R&B and soul music, for one, was still pretty much a singles game as the '60s turned into the '70s. But then, right at the turn of the decade, something happened with Curtis Mayfield and Marvin Gaye and Stevie Wonder. Even James Brown, who was responsible for some of the best singles of the '60s, began making albums that were great – and carried a common theme – from start to finish.
