Because health officials and scientists don't care if they are wrong with their forecasts. They don't want to be right. Because if they're right, the end of the world comes with the disease and hundreds of thousands, if not millions, die. So they will always push forecasts and models to show catastrophe. People who are elected or hired to make decisions for the benefit of all people need to understand this and see both sides of the story and know that if they make errors, real people suffer and the economy is destroyed.
It is understanding that a narrative is being pushed. It is OK to push a narrative if the people making the decisions understand that it is a narrative and not necessarily the truth. The problem is that our leadership is severely lacking and goes with the media pressure that is pushing a different narrative - one that is politically aligned with success for their party.
So you've got scientists genuinely concerned about a disease but not caring about anything other than stemming the tide of the disease who exaggerate its danger to do what they can to stem the tide. Then you have the media latching on to this and saying "lets destroy the economy because that will be bad for Trump.". Then you have all sorts of Modern Monetary Theory seizing upon the opportunity to get the Fed to bail everyone out and established policy that would otherwise be considered lunacy, but now is considered "necessary". All of these people pushing their own narratives.
A real leader would be able to have them all at the table and would be strong enough to say "sorry, I understand the risks you are presenting but you aren't seeing the big picture here." and push back. But we don't have real leaders anymore. So we act like a herd of gazelle spooked by the sight of a leopard in the weeds. That's all we are.