Because the answer is, we wont know for sure until it's over. But you can lessen the impact on economy help with bring it back, western countries produce more

Because the answer is, we wont know for sure until it's over. But you can lessen the impact on economy help with bring it back, western countries produce more than enough food to make sure nobody starves (if they want) If you leave covid 19 unchecked it will overwhelm your medical system anyway so even more people would loose access to medical care. So the choice comes down to, hope that worst case (italy++) wont happen and carry on, or try to do something. And you cant get away with bulshit pretending that you are doing something when you are not, because people suddenly listen to scientist and doctors, when their ass is on the line. Unsurprisingly we choose to do something. Additionally given that in west most politicians are elected, and that most reliable voters and donors for political campaigns are from age group most affected by this virus, decision is even more obvious.