Because it is not a reliable news source. Because it does not rely on professional journalism. Because if Breitbart reported that grass is green, you would still need another, more serious, source before you could know that is actually true. Because even though it is slightly better than QAnon and NewsMax, the emphasis there is on "slightly". That is what is called (very) "faint praise". Need I go on?
Dear Lord. We have gotten to the point where Breitbart can be described as "slightly better than". Who would have imagined we would sink this low in just four years?
Here's a better idea: You cited Breitbart. Tell us why - other than confirmation bias - you find it reliable.
The guy made a statement as fact..let him back it up. For my part I find it reliable because they follow the facts. Take the FBI lawyer who just flipped and admitted to falsifying emails to obtain a FISA warrant. They've been reporting on this scandal for 2 years. Why have the mainstream media not been? That's only one example.
The facts that fit your narrative, you mean. A Google search shows that all of the mainstream media have covered the story. They just don't happen to spin it the way you'd like it.
I try to stay away from partisan sites like Breitbart or DailyKos because they are nothing more than rags that twist stories to fit their narrative. Plus people who digest that crap on a daily basis tend to be the most hateful people on the face of the planet.