The reason that boxers wear mouth guard are usually for protection from around the mouth from the research I have made, at least from the blog and few websites I visited
Different types mouth guards
https://blog.awma.com/5-reasons-mouth-guards-should-be-worn-in-martial-arts/https://harderpunch.com/why-do-boxers-wear-mouth-guards/However, beyond the reasons we have reviewed above, my hypothesis is therefore that I think the reasons are not only for physical protection but for psychology protection on the ring
So you think the only reason that boxer wear mouth guard is to avoid bitting?
No, I don't think so.
I think it also extends to avoid them from cursing , from using abusive and fowl words on their opponent.
If this is the case, I think maybe it makes the opponent to get more provoked and angry as anger has a way of making someone lose balance and control.
If this is the case, I think by instructing the wearing of mouth guard as a rule, either the officials are trying to avoid the boxers from being more exposed to blows because they can go out of focused and concentration. Here, I think is not because of the rules of the game not to be violated but to help the opponent guard themselves because it will be chance or advantage for the opponent who is coursing to attack more.
In sighting example, you could relate this with Muhammad Ali in his fighting days tried everything he could to muta some words to his opportunity and that further provoked them on one side or frustrate them because they kind of lose focus
I think this my phycho-political hypothesis can go a long way to help you think deeply on the reasons they cover their mouth beyond just avoiding dental damage.
This is a self made hypothesis from a deep thought.