The problem is that most journalists are innumerate. As Matt Yglesias notes, "many reporters and editors don't really understand what they're doing. Reputable colleges hand out degrees to people who have almost no understanding of quantitative methods." [1] These journalists see the numbers as garnishes on a narrative point. They're not trying to put the numbers in some sort of mathematical context to draw sound conclusions. They may not even realize that there is a difference between using numbers for garnish and deriving meaning from numbers.
[1] https://www.theatlantic.com/politics/archive/2007/12/innumer....