As much as it's stupid for the Feds to only finger NJ (since as noted in the article Delaware, Pennsylvania, California, and Utah also use cutesy messages on their variable message signs), ideally the VMSes should be used to provide useful information for the traveler. If the signs are always going to display a safety message, whether a generic one or cutesy one, people will begin to ignore them after seeing the same "Buckle up" messages over a over. Then when there is a useful reason for the sign to be used (e.g. Amber/silver alert, incident ahead), they will be ignored.

I think that is what the FHWA is going after in this case. They are very stringent about enforcing MUTCD guidelines, at least for federally funded road projects or state agencies. A few years ago, Andrew Cuomo spearheaded those stupid "Taste NY" and the like signs but had to be modified because the signs directed travelers to a URL to download an app. Local agencies are better insulated from the feds, which is why illegal blue lines within the center lines still persist on county and local roads. (note the irony of the location of this blue line)