When PBS stations went on the air in 1970, there was a need for public broadcasting. There were only three major networks and many areas were not served with local TV or TV news. There was not a sinble TV station, for example, that was licensed in New Jersey -- New Jersey residents got their TV from New York and Philadelphia. Publc television was welcomed.
That's not the case today. We have plenty of choices and there's no need for taxpayers to fund TV and radio. It's not even commercial-free anymore, because corporate sponsors want a little more air time for their money. If you want truly commercial free radio and TV, you subscribe to cable or satellite services.