The official advice regarding masks seems to be don't need it unless you're sick.
I mean the first problem with this statement is that you don't actually know that you're sick. Then if you look at China and Korea and Hong Kong and all these countries that seem to be doing a good job at containing this virus, every single person is wearing a mask. Not just people on the street but politicians, reports, scientists and doctors etc.
Are they wrong? Are they all just overly paranoid? Do we have a right to judge when they've managed to contain this virus?
Are the advice to not wear masks just because there is a shortage of masks and that if there wasn't a shortage we should all wear one? If this is true, is that not absolutely crazy? The Chinese were able to supply masks for every one of their 1 billion+ ppl and we've had 4 months and not been able to find 30 million masks for our population?
mask is also useful in repelling those people.