From a marketing and profit point of view, I just don’t understand why ABC/CBS/NBC still hang onto their news departments. Their viewship, and ad revenue, is dramatically down and never to be regained. I would think that could find some other type of programming during the news segment that would generate greater ad revenue.
This is not my area of law or expertise, but I believe that the federal government demands that "X" amount of hours of broadcasting be broadcast "in the public interest" if these companies are to retain their broadcast license. I don't know if "news" is specifically mentioned in statute, or in case law, but I think the broadcast networks have at least some legal obligation to broadcast a "news" program".
This was reinforced at some point - again, I think - in the late 60's when the FCC gave the networks some additional time to broadcast commercials during each hour. The networks agreed to children's programming and news or other public interest programming requirements for that extra time.
Having said that, NBC still makes a TON of money off news, and ABC/CBS still make money, not just the kind of money they'd like. It's not a "loser" , yet.