Or they report on what they think people would be interested in. I suppose that's a bias but it's an suspicious use of the word.
Biases become a problem if a person has one and doesn't take it into account when making a decision. The news is making the coverage decision not the person with the bias unless you count an indirect viewership loss that may occur.
Agreed. I think the newscaster joke in arrested development was a solid demonstration of this point. For those who don't know it, the showrunners would frequently insert a news clip of the same reporter summarizing whatever silly plot was going on, ending with: "What this means for your weekend, at 10."
Honestly that's what people watch the news for. What are external factors that they were previously unaware of that might impact their lives (or weekends)? Most (not all) people are aware of the dangers posed by heart disease. They're not watching the news to learn about something they're already aware of.
I might be beating this horse to a second death, but there's a section of road near where I live that's dangerous, and we all know it's dangerous. It's not newsworthy. If another section of road collapsed and introduced a new danger, then that's newsworthy. News is newsworthy because it's new and unfamiliar. If something is reported on that's old and unfamiliar, then that's a documentary. If it's new and familiar, then that's a paradox. Or maybe a fun anecdote at a party.
All you're saying is that the news coverage is a reflection of the biases people have (like the one above).