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.
Not really, I mean if you WANT to wear a mask you should have the freedom to do so, but don't come to me forcing me to wear that shit when I am perfectly healthy.
What's your opinion of drunk driving laws? That analogy occurred to me the other day. You could say, if you want to get drunk and drive home, you should have the freedom to do so. But the drunk driving laws are there to protect OTHERS, not the person involved. The same logic is currently being used for masks, rightly or wrongly. So you aren't being asked to wear a mask for your own benefit, but for the benefit of others (just like you are asked to not dive drunk for the benefit of others). IF they were effective in that regard, would you then support a mask mandate?
False equivalence. Driving under the influence of alcohol can impair your motor skills making you incapable of operating the vehicle, which in turn can result in self bodily harm, harm of others, and damaging of state and city infrastructures. The Mask on the other hand tells you right on the box it doesn't protect you from Covid-19.