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.
My first thought was yeah! Bam! And then I thought, it's the same. If a mask helps people sleep at night, let them CHOOSE to wear one. If I have a mask on my face and almost have a panic attack, and don't believe in one, let me CHOOSE not to wear one. Some people steal children... I chose to see my children's faces so they are harder to take, plus the mental hardships resulting in not seeing faces is awful. Satan wants a life without choice. A life without choice and freedom is no life for me.