At one time every network, TV, radio, newspaper, had a news bureau. Small news outlets had local and statewide bureaus. Mid-sized one had nationwide setup with offices in NYC, Miami, Chicago, LA. Large networks maintained offices in capitals and major cities worldwide. Much of the international flavor of major cities like Moscow, London, Paris, Bangkok, and many other cities, came from news services maintaining offices there.
There was a whole lot of redundancy because CBS, ABC and NBC all had their own people and networks. NYT. LA Times and Washington Post all had their own networks. Then you had both the API and UPI press services. Pretty much every story and every angle, with a few notable exceptions, like FDR's polio, got covered as all these organizations competed to get the story and get it first. It also helper that reporters had very little loyalty so they moved moved to organizations that would get their stories out.
It was also a time of accountability for news. Facts tended to get out as any organization that shaded its coverage got undercut by another service. There were only three main TV networks but radio had hundreds of independent stations and newspapers were numerous. Even small cities had two or three newspapers. Large cities often had three or four major papers, four or five regional papers, and many minor ones. And every single outlet dreamed of breaking 'the big story'.
The other thing you need to understand that news bureaus for TV and radio were seldom profitable. Newspapers made their profits on advertising and classifieds but TV and radio consistently lost money on news. But, conventional wisdom was that if you ran a network you needed news. The 6 o'clock news was the lead into prime time and ratings that allowed you to charge the big bucks to advertisers. It was also a point of pride to have a news department that got he story first, got it right, was seen as honest and reliable. CBS made its bones in the 60s with its coverage of the space program.
What changed was that the news department went from being seen as a status center to being just another profit center. News had to start to show a profit on the money invested. So the expensive parts, like maintaining bureaus in major cities, and particularly foreign bureaus, got liquidated. News departments shrank and, in a lot of places, ceased to exist. Local TV stations don't often have actual news departments. They get something from a news service and regurgitate it. Which is why, if you pay attention, you can go see the exact same phrases used time and again across networks and papers. Instead of there being two or three reporters giving accounts that differ so there is a verification and nuance we get one account that may or may not ask the key questions and cover important aspects.
With news departments required to show a profit the news has also shifted to celebrity gossip and fluff pieces. Those sorts of reports are cheap and easy to get and you have a built in audience. So we get five minutes on Paris Hilton flashing her vajay-jay and Justin Bieber's new haircut and thirty seconds reporting on the airliner that went down.
Then there is media consolidation and the lack of accountability it allows.