Editorial bias has been the norm through most of our history. Knowing who is reading your paper is important to know, because that is how you court advertisers. And catering to those readers is how you increase circulation so that you can charge those advertisers more.

Now, for most of the 2nd half of the 20th century, this bias was, for the most part, confined to the opinion pages. The hard news sections tended to avoid editorializing in their stories. However, in the digital age, the economic pressure is just too great to not cater a lot more blatantly to viewers/readers.