Because nothing in the world is perfect, and by acknowledging that you and others all have implicit and explicit biases you can use your critical thinking skills to learn about the world without blindly accepting other people's biases as your own?
When people say something is biased, they usually mean to an unreasonably high degree. As you say, the nature of the universe dictates that everything is biased in some way. While a news source inevitably has to pick and choose what stories it's going to report, most people would not consider it "biased" if it simply reported what events occurred and did not take place in writing opinion pieces. On the other hand people consider news to be biased when it skews too far towards editorializing content and telling people how they should interpret reality.
Take for instance every time the POTUS makes a speech, and I'm talking about presidents long before Trump; as soon as they stop speaking, every new station cuts to a group of pundits to tell you how you should interpret what the president just said. It's not journalism at all, and anyone who pays attention to politics a lot would be just as qualified to be a pundit. Why should anyone trust that level of bias over what was actually said? If the opinions of political junkies are more important than what was said, then we're basically screwed because it's not the people who decide how to view events, but it's news organizations who pay people to dictate opinion that create the narrative around events.
Yes, you can certainly sift through bias using critical thinking skills, but this only gets you so far when the news itself becomes more bias than actual reporting. We don't live in a perfect world where everyone is capable of critical thinking. If we did, then almost everyone would shut off the TV as soon as the president is done speaking. Instead, we live in an imperfect world where having highly biased news is really dangerous for a society that hasn't proven to be capable of coming up with its own perspectives when other perspectives are being foisted upon them by the press and the state.
>as soon as they stop speaking, every new station cuts to a group of pundits to tell you how you should interpret what the president just said. It's not journalism at all
I disagree entirely. That is the essence of journalism. Not to tell you what to think, but to provide context that helps interpret.
For example, reporting that people at a Trump rally were shouting "Lugenpresse" is one thing. Providing the historical context that such language was used by the Nazi's as a pretext for cracking down on the free press and on Jews is another. Just hearing the first may make you aware of a fact, but the second tells you the truth.
