I think the idea is that you aren't putting your dirty fingers in your mouth, or your spit on stuff that other people might handle. The latter really doesn't matter scientifically I think, but the former probably does.
People put their fingers on all kinds of things other people have touched: doorknobs, elevator buttons, shopping basket/cart handles, etc. Adding a moist pad to that isn't going to change anything. Keeping people's hands out of their mouths, however, might.
People put their fingers on all kinds of things other people have touched: doorknobs, elevator buttons, shopping basket/cart handles, etc. Adding a moist pad to that isn't going to change anything. Keeping people's hands out of their mouths, however, might.