Because science.
edit: after reading so many thoughtful comments, I am changing my view on this matter. If you are sick, and go out in public, please be kind and don't spread your germs everywhere. If this means wearing a mask for you, then God bless you. If you choose for whatever reason to not wear a mask, then God bless you and you should be free to decide that. If you go out in public, you assume risks that there are germs out there. If you are not comfortable with those risks, you have the right to no go out. If you are a business, you should not be required to put up any signs or enforce any such orders. In fact, there shouldn't even be such orders. In other words, let's just go back to the way things were. This may mean imposing a BAN on requiring masks not a ban on the masks themselves. Thanks all for the lively discussion.
your username makes the counter-arguement
I see your point, but masks are counter to the interests of the common good, which is why laws exist. With a mask, you can more easily hide your identity making crimes easier to get away with. Not to mention human trafficking which isn’t just a crime, it is an affront to humanity. Since they have no medical value, they should not be allowed. Exemptions available for disabilities, etc, of course.
edit: point taken and I agree
So because criminals exist people shouldn't be free to wear a mask on their face? Sort of like banning guns because bad people shoot people?
this
Restrict freedoms for the “common good”. Geez, that sounds like a leftist argument.
All laws restrict freedoms for the common good. Are you saying there should be no laws?
There's masks for the masses, and there's masks for the medical profession. Ask any doctor about wearing masks in a hospital ... that has been going on for decades and they have never complained (and they are ... doctors ... ). This idea that masks have no value to anyone anywhere is a dangerous extension of a core idea.
Plenty of actual research shows masks are counterproductive in hospital settings. We are bio organisms designed to breathe through nose and mouth.
They're effective to keep the doctor's saliva droplets while speaking from getting inside a patient who's undergoing surgery. That's the main purpose.