Doctors *do not* wear them all the time, and when they do, they change masks frequently. Why? Because of germs. Bacteria. Because they're filthy things. Any honest doctor will tell you they are against extended mask wearing. One of my brothers told me recently he saw a man take off his mask, wipe his sweaty face with it, then put it back on. Masks are disgusting things. You know you are not supposed to touch them once on, you're not supposed to put them in your pocket or handbag... guess why.