I'm sorry, I'll add to my reasoning for why they are pointless (unless it's the n95 originally stated) and why you shouldn't wear one...
First, people fidget with them. Adjusting, pulling up and down, and not washing them before re-use only adds bacteria and viruses from what you come in contact with. And I'm positive people don't wash their hands before touching the mask.
Second, people don't wear them properly rendering them completely ineffective.
Third, by doing the first point, you basically created a petri dish against your face. That allows bacteria, viruses, and spores to grow from the moist heat escaping your mouth and nose. Once said particles break off and enter your lungs, you can have problems such as pneumonia, rsv, rhinovirus, bronchitis, and other respiratory illnesses.