Let's see how we got here. When I was young in Sydney, there was radio station 2SM and CountDown. Who could forget?
2SM was the radio station that played all the Top 40 hits and since there were so few stations in the 70s, it was youth radio. It was decimated when FM arrived around 1980 offering far better sound but the licensing arrangements didn't allow them to transfer to the new band at the time.
CountDown was the TV music show of its day and made Molly Meldrum a household name in Australia. It was on the ABC (Australian Broadcasting Commission, roughly the equivalent of PBS and NPR rolled into one). Since it had national reach, none of the commercial stations could effectively compete and it was the launch pad for many bands. The show ended almost every week with a countdown of the top 10 (hence the name) culminating in playing the film clip for number 1 I say "almost" because Abba's "Fernando" was #1 for so long that everyone got sick of it and they stopped playing it! Did you see the 20th anniversary show in 1993? It was a blast!
ABC radio launched 2JJ or Double J with Skyhooks song "You just like me because I'm good in bed". It set the pattern for cutting-edge, provocative music programming and being government, it was mercifully free of advertising. Double J became Triple J with the move to FM. Often they played garbage because it was new and different but there were gems thrown in and it was up to the audience to decide which was which. Rap was played years earlier on Triple J than any of the commercial stations.
The tradition continues, more or less. I believe they have a playlist now (they didn't in the early days) but there is little overlap with the commercial stations. Sometimes this is good as it avoids endlessly- repeated, over-packaged American pop but it also means you need to listen to the commercial stations some of the time just to find out what's happening in the outside world where there is some endless-repeated, good Australian music.