Because it doesn't mean anything. No large company will respond to supply chain questions.
> But are you store employee or a corporate headquarters employee?
What is the relevance?
One of the points of the article is that corporate isn't aware of these problems.
Let's take this from the other side. Your employees have gone to the press, and the press is asking you for your side of the story. Why would you give the press anything to write about? Pictures of empty shelves have much more impact than in-stock statistics. You clam up, try to find the employee (probably disgruntled) and terminate him/her.
In other words, corporate not responding is not a signal one way or another, it's the sign of a mature company. Not to kick a dog, but Uber might have responded and made things worse.