Because it went onto a popular internet website. And really in the internet age ALL news is national, because it all winds up on websites read by people all over.
I’m glad it’s national news. These idiots need to be outed...er...revealed...er, nevermind.
Because it's news you can use.
Some times it helps people to be reminded in a roundabout way, "what not to do", professionally or otherwise.
From the thread's comments, Subway lost some business, however, the remaining employees, and let's face it, some of which may not be the swiftest people around, will possibly pause before at least engaging in such unhygienic behavior, let alone posting actionable documentation.
(Well, probably not. Weiner didn't learn, but he's an entitled Dem hack.)
There are probably legal, not to mention marketing, reasons for making sure that it is known that Subway takes the integrity of its ingredients seriously.
As for the national news, it's an out-of-the-norm story that used to be relegated to "R" and "blue" movies. "Journalists" and editors used to sell their souls for a titillating story (unless it interfered with their political miasma).
Way back when, Paul Harvey reported on an instance of the then-"fad" of sitting butt-naked on a xerox, and making a copy or three.
His story had a woman getting fired for doing same.
Later, Harvey got more mileage out of the story by reading a listener's letter commenting on the original story, saying the woman "... was fired for getting a little behind in her work."