Socially Acceptable

The other day, a friend asked if applying deodorant in a public space was socially acceptable and the consensus was that it was definitely socially unacceptable. We have deemed certain things to be acceptable in public spaces but others are not. Just as applying deodorant in public is unacceptable, using nail clippers in public is also greatly frowned upon. Filing your nails in public is generally acceptable, but digging dirt from under your nails is not. Grooming your hair with your fingers is acceptable, but using a comb or brush on your hair in public is not. In the US, using a toothpick to remove food from between your teeth in public is greatly frowned upon, but in many other cultures, it is acceptable to do so. Applying lotion to your hands in public is acceptable, but applying lotion to your face is not. Flossing your teeth in public is highly unacceptable. So how do we decide that certain elements of personal care and grooming are acceptable in public spaces but others are not? Why are there certain circumstances when normally unacceptable behaviors are fully acceptable?