[pavelrub]

I haven't seen any evidence supporting the argument that they do not protect the wearer. The argument seems to be that they aren't 100% effective at that, and therefore shouldn't be used for those purposes, which doesn't make any sense. Even 20% reduction in the amount of incoming droplets is significant - both for protecting the wearer, and for reducing R0.

[kevingadd]

Part of the reasoning is that people who believe masks provide them full protection will take more risks than otherwise. Combine that with hoarding and other behaviors and it's possible that promoting widespread use of masks would cause new problems the west doesn't already have.

If we had successfully promoted "wear a mask when you're sick" as general US policy in advance we probably wouldn't have these supply chain issues and it would be safe to advise people just wear a mask at all times during the crisis. We didn't, so most people don't have any masks, which means they're going to look at this crisis + advisory and panic buy a big pile of them when supplies are already limited.