1. Experts are afraid that people use masks as a kind of "get out of jail" -card and start doing stupid things if experts say masks make you safer, thus discounting any benefit gained by using them in the first place. 2. Experts are afraid that widespread usage of masks causes supply issues for health care workers where they are needed more. 3. Governments are worried that making masks socially acceptable cause trouble for their facial recognition dystopian dreams.
Or something else. Can anyone ELI5?
1) To stop the wearing being infected by other people.
2) To stop an infected wearer spreading their infection to other people.
Experts recommend against masks because:
When correctly put on, and worn, and taken off there's some protective value to masks if they're combined with all the other PPE.
Correctly putting on PPE, and correctly taking it off, is hard. Healthcare providers employ staff to act as "spotters" or "dofficers". This person's main job is to help people put on and take off PPE.
If you're wearing a mask by itself you get almost no benefit. You lose all benefit if you're putting it on wrong, or taking it of wrong, or wearing it wrong.
As well as that we see that masks increase risky behaviour. People wearing masks feel that they don't need to maintain 2 metres social distance. It's hard to speak through a mask and it's hard to hear someone talk through a mask so people both speak louder (generating more droplets) and move closer (increasing the risk of contamination).
People who advocate against masks look at the evidence which shows marginal benefits from mask wearing and they look at all the things which reduce or negate those benefits and they say that the balance tips away from wearing masks.
Whether you wear a mask or not you need to keep 2 meters away from people, so what does wearing a mask get you?
https://www.economist.com/science-and-technology/2020/04/11/...
(1) Using mask to protect oneself from covid-19 in public spaces. Experts don't see this working effectively. Doctors and nurses don't use masks outside the infectious zones in hospital either. Using mask properly and donning and undonnign it is hard. Men have to trim their beards and the mask must have clip that goes around nose etc. You want N95 mask if possible, and it's hard to breath trough it so people leave gaps so that breathing is easier. Old people just can't breathe trough N95 outside. It's too tiring.
(2) Using mask to protect others from covid-19. This is where mask can be helpful in widespread use. It slows down or catches most droplets. Just cheap surgical mask or just a scarf can be enough (remember: surgical masks protect the patient in surgery from those wearing it, not other way around). Additional benefit is that covering your face prevents you from touching it.
There may be no evidence of wearing masks causing harm to the wearer, but there is ample evidence of excessive demand for masks leading to health workers not having adequate protection. That, along with "no evidence of masks preventing infection in the general public" is enough, I think, to justify the current expert opinion.
I would not normally be wearing a mask outside at the moment because there is no compelling medical reason, as far as I can see. As long as you maintain distance and wash hands, etc. However, I do wear a mask outside because I live in a country where an unmasked foreigner causes "concern" to some. So I mask up for social reasons.
My understanding is that it is a variant of 1. Masks probably do help, but the general population would not use them correctly. Anecdotally, I saw this a lot going to the grocery store yesterday. For example, people were constantly fidgeting with their masks and removing the masks to talk to other people.
From what I've read, its also early on so there weren't a lot of studies about how to prevent.