Personally, as a non-LEO I don't attract undue attention to myself to require a need for a "deterrent." If I am confronted with a situation which requires de-escalation then my mouth should work pretty well. If not, then I have hands, elbows, knees, and steel toes. If one feels the need to make such a situation easier and sway the "odds" in their favor then high power stun guns or batons are excellent and will always incapacitate for a while. Excessive? Guess the guy should have listened to my mouth in the first place.
OC is also great against dogs.They dont always listen to your words when they are really angry.
I think postal workers have OC issued to them for that reason.
I think OC is not the answer for everything but it's a great tool in some situations.
I live in a rural area and I think that I have more chances to use my spray against a dog than against a human attacker in the city.
If im attacked by my neighbor's dog I dont want to have to crack his skull open with a baton.Usually just spraying the dog from a distance will make him leave.
And like you said in some situations the use of empty hands techniques or baton would be better than OC, like in case of knife attack and such.