A focus toward young adults doesn't mean no teens were listening. Even before that, certainly there was no expectation that teens were buying cars from Merolis Chevrolet or buying the week's groceries at Farmer Jack's.Again, not something young adults would notice even though they listened to Top 40 radio stations.
And, as a person whose first radio job was at an all-jazz FM in a major market, I can say that such preferences put you in a very small segment of the population.