Non-experts have no credibility to lose, nobody remembers or cares when their predictions are wrong. So what's the risk in concluding before you have all the data?

Experts are pinning their credibility on the line - not even if they issue every guess under a giant glowing banner saying "THIS IS JUST A GUESS WE DO NOT HAVE THE DATA TO BE DEFINITIVE YET". So: they're slower. I am not, incidentally, saying WHO's response is perfect.