It's because they been taken to court for mindlessly parroting shit they hear, but instead of actually verifying the truth of the claim (ya know, the entire purpose of a journalist) they just put it in quotes as some kind of "buyer beware" disclaimer

Journalism is just as much reporting what different influential people say, whether the underlying statement is true or not.

> actually verifying the truth

That's the job of the reader, not the journalist. Unless you're living under oppression. So you have misunderstood the purpose of reporting.