I don't love the 500lb gorillas of mainstream media, but they have skin in the game if they get caught pushing falsehood. Look at men who've trainwrecked their careers over getting caught in a lie - Olbermann, Dan Rather, etc.
Can you imagine smaller no-name media sources facing any real consequences in that kind of situation? No.
We need credibility again. Until somebody finds a way to algorithmize credibility, I'm happy with saying "only the big boys are assumed to be credible by aggregators".
To make it easier for people to accept the premise, let's suppose that we are not concerned about the United States. Say we are worried about some other countries.
The issue is that when only a relatively small number of the largest media companies show up in the results, that makes it easier for state or corporate interests to control the information stream that citizens receive. If smaller, independent outlets were surfaced more often, it would mean that in order to push any particular narrative effectively, there would be that many more media outlets to control. It could make it much more difficult for a government or special interest to propagandize, since they would need to influence a very large number of independent outlets.
And again I realize that many people here may not believe that government propaganda still exists in American media. But I think that most can agree that it does happen in many other countries at least.
But because smaller media sources are forgettable and have fewer eyeballs checking them, there's no record when they do something unethical like the large companies.
Rathergate would not happen with some small, forgettable news source. The falsehood would be pushed and unquestioned because nobody wants to play whack-a-mole.
The 'big boys' have more than enough bias, and tricks up their sleeve to bend the story to their liking.
Also, the current government under Trump despises most of the big boys for obvious reason, so pretending they constantly push government narratives again highlights quite a distorted sense of reality.
Just look at Pulitzers awarded for the Collusion story that's been proven to be fake. Or the anti-semitic cartoon they were forced to withdraw last month.
Somebody may have told you they were fake, but you should stop listening to them and go read the stories yourself.