This is the key really - the various rating systems for masks were developed with ingress, not egress in mind - they're PPE first and foremost. When studied, it's been found that pretty much any level of mask, homemade, surgical, construction and so on, all reduce droplet expulsion to varying degrees. In a situation like this, where the pandemic is in action, people doing what they can to flatten the curve, reduce exposure etc. "every little helps"
And another thing - this is completely anecdotal - but I reckon if more people started wearing them then more people would remember to take, o