Like most things, I don't think there's only one right answer. Realistically, most non-news/talk stations abdicated whatever news/information obligation they might have felt long ago. That ship has probably sailed.
As a result, most people don't look to radio to stay informed anymore.
That said, the most idealized sense of obligation a station would have to keep the public informed would depend on their audience and the topic at hand.
If the audience gets "informed" from other sources already, then the station can't really be obligated to meet their needs again. Unless they can make it easier for the listeners to get informed, or offer something the audience doesn't already get.
If the audience doesn't get "informed" then the station should probably figure out why they aren't informed. If they aren't informed because they don't want to be informed, then it's going to be a long, unrealistic road to informing them.
Overall, whatever a station can do to meet whatever needs their listeners have can almost always be good, though.
