Although I have been following this case closely, I cannot recall if LE has made an actual plea to the public for information/help recently. I simply cannot find the most recent articles.
It seems that, when they really have no information at all, LE resorts to pleas to the public. If they have leads, however, they seem to keep quiet to protect the investigation. They may not release video, etc. They may not want anything to interfere with their investigation. When they truly have nothing, it seems that large search parties are gathered (whether by LE or family and friends). I tend to agree that they may not want to tip off anyone who may be a POI.
I agree that this has been odd from the very beginning, and I do hope it's because they have promising information.