Another personal anecdote. A few years ago I found myself in Scotland. One night I entered a small pub and started talking music with the locals. The British pop charts were full of 50s and 60s soul, and everything old was new again. So it wasn't just an American radio thing, I mused.
Radio dictates people's narrow listening habits worldwide.
The last bastions of radio diversity are National Public Radio and college stations. Both are committed to broadcasting rarely heard material, NPR concentrating on the old, and college stations concentrating on the new. They're to be applauded for not playing the same old thing. The key, I'll cynically point out, is money. Neither format has its major funding come from advertising dollars.