[beatgammit]

Masks are effective at preventing spread to others, but they're fairly ineffective at preventing spread to the wearer since the virus can get on any exposed skin and make it's way to your mouth (e.g. touching after washing hands) within the 3 hours or so it can survive.

Since we don't know who is contagious, and we don't have enough masks for everyone, they're essentially "useless". They're quite useful for medical professionals because they're more likely to use sufficient caution than the average person, so it makes sense to reduce panic buying for something that likely won't help the average person so more are available for those that really need it.