Unclear concept

I've seen a number of signs in different places of business telling people "if you are vaccinated, feel free to enter without a mask. But if you are unvaccinated you need to wear a mask."

What baffles me is the fact that I am wearing a mask to protect others. Not to protect myself - that's the nature of a virus.

So telling the vaccinated to go about their business is the opposite of how this is supposed to work.

But that's Murica for you I guess.