InternetJeff Network News can be deemed essential by it’s network for pride and branding, so I can see that being paid for out of overhead (a little business lingo there).
And I don’t know if this applies to the networks, or only the local stations (that actually broadcast over the air), but these news programs probably help them meet their licensing requirements.
For using public airwaves, broadcast licenses require operators to serve the “public interest, convenience, and necessity,” meaning that broadcasters must provide programming that is responsive to the needs of the communities that they serve. This can include local news, educational programs, etc.