Because that would be admitting that they don’t have a clue. Literally.
Just throwing that out there BTW, have no idea but I would not surprise me in the least that the government could have leads that compromise diplomatic “natures” and do not want to address this now (For public consumption).
It would be interesting to see a breakdown of the time wasted ‘training’ on PC nonsense like avoiding racial profiling, sexual harassment, a gay-friendly workplace, etc.
J. Edgar Hoover would hang his head in shame at the state of federal law enforcement, who are big on paramilitary gear, hi-viz vests, press conferences and so forth but who seem to lack any sort of personal or collective initiative - i.e. proper detective skills - in narrowing a search quickly. They do love their press conferences and fifty-cent words, though.
When they have a case to build, they are mum. As you say, their embarrassing public pleas for help are a tacit admission that despite loads of evidence dropped into their laps via the modern fetish for video recording anything and everything, they are throwing their hands up less than a week after the incident.
I'm still hoping that they are looking like Barney Fife to get the perps to drop their guard and come out of hiding.
I still can't understand how with all of that photography and surveliance tape they aren't closer.