Wasting the wearers money on something that is not beneficial
Making the wearer carry around something they don't want or need
Concealing the fact your next date may have no teeth (that may be a good or bad thing to some).
Increasing the chances for a wearer to develop a bacterial respiratory infection that can transform into pneumonia, bronchitis or even pseudo neuragnial vagitosis of the soft palate while saginally shifted inside the cervix of the uterine sponge lotus valve.
Masks are GOOD at: