Bullheaded wife/Covid

The part I don't get is the N95 mask protects the caregiver from getting a virus and is 95% effective. Why can't it protect a regular Joe? If it is fitted properly and you don't futz with it once it's on. It seems the mask is discouraged because there is a shortage.

I used to work in a water treatment plant , they had every kind of mask that is made, cant remeber the names or numbers of them, some were the best that can be had /for chlorine leaks and , or maintainence . None of them ever fit me good enough to where I wanted to work in the chlorine room for any reason , in fact , I hated even going in the chemical bldg .