you having direct transmission contact to your two key entry points which are nose and mouth. Anything that can slow that, is better than nothing, which is why homemade, washable masks are useful as well.
The example I used for my daughter is from my hay hauling days.
With mask, ring around my nose and mouth all green and dusty at the end of the day
Without mask, washing, picking green boogers and hacking up green loogies until the next morning when we start all over.