A load of people in this thread are saying the CDC (and others) are lying about masks.
For members of the public walking around a mask provides at best marginal benefit, and that's only if the wearer complies with a strict regime of donning and doffing protocols, and if it's combined with a full set of other PPE (disposable gowns, gloves, eye shields) and frequent handwashing.
As soon as you drop any of those you're not just making the mask a bit less effective, you're probably increasing the risk over not wearing a mask at all.
There are a few routes of transmission -
fecal oral; fomites to hand and then to eyes, nose, or mouth; and droplets landing on your eyes or being breathed in.
It's likely that in members of the public the main route is touching an infected surface and then touching your eyes, nose or mouth. Masks only help with breathing in droplets, and they only help if they're worn correctly. Incorrect mask wearing increases risk because masks feel weird and cause people to touch their face more often, and because masks give permission to people to go outside and mingle in crowds.
There's not much research around whether members of the public can wear PPE correctly, but there's plenty of research around PPE and healthcare professionals. We know that qualified registered healthcare professionals who know the consequences of not wearing PPE correctly still struggle to do it all correctly.
> Most people aren't idiots - if the masks help protect medical professionals from Covid-19, they can also help non-medical professionals.
The difference is that healthcare professionals spend all day in close contact with symptomatic people and are more likely to come into contact with blood or fecal matter or sputum, and are more likely to be doing aerosol-generating procedures, so the baseline risk is much higher, so that marginal benefit turns into an actual benefit. But importantly they're not just wearing masks. They're wearing gowns and gloves and eye protection and they have access to water and soap and alcohol hand gels and infection control teams to train them on how to wear it correctly.
Here's what HCPs are wearing. Are you honestly suggesting this for members of the public? https://twitter.com/QEGateshead/status/1244208756600307712
Here's a simple graphic for donning: https://twitter.com/agtruesdell/status/1245470479059767297?s...
Here's a thread talking about donning, wearing, and doffing PPE. https://twitter.com/halletjulie/status/1245409318775767042?s...
This is not the CDC / WHO / etc lying, this is them talking about the science as they understand it. https://twitter.com/shinybluedress/status/124277978004452147...
> even a bandana can likely help prevent disease transmission
You're basing this on a small study carried out in a lab using research bacteria (not viruses) carried in a calibrated spray, that didn't include "people breathing through the mask". You've massively overstated those results.