They incentivize the laziest kind of writing, truly a wonderful gift to pundits. If a politician's approval rating changes even a small amount you can just do some hand-waiving and chalk it up to some minor event from a week ago that caught almost nobody's attention.
Also sometimes you get a pattern where some tracking polls consistently find approval numbers in slightly different ranges compared to others, really just making it easier to write whatever Take you want.
Anyways the "dip" in this Hill-HarrisX poll is a whopping 2 points from a week and a half ago.