I have been asking myself the same question. I think it comes down to two reasons:
1. Masks are in short supply and they believed they could save them for healthcare workers by convincing the general population they don't work.
2. If you are measuring efficacy, the general population won't reach the same level as a healthcare worker because they have not been professionally fitted and trained in on/off procedures. So instead of reducing risk by 95% the average person would see something like a 70% reduction, and they decided "perfect is better than good enough".
1. Masks are in short supply and they believed they could save them for healthcare workers by convincing the general population they don't work.
2. If you are measuring efficacy, the general population won't reach the same level as a healthcare worker because they have not been professionally fitted and trained in on/off procedures. So instead of reducing risk by 95% the average person would see something like a 70% reduction, and they decided "perfect is better than good enough".