Why do people bite other people?

In most cases, people don't bite each other. But as little children, biting is often a way to show anger and frustration; children throwing a temper tantrum may try to bite the adult with whom they are upset. But adults who bite other people are rare-- there are little "love bites" which may occur during intense sexual activity, but I assume these are not the kinds of bites you are asking about.

Adults who intentionally bite another person are generally in the midst of a mental illness, or perhaps trying to escape from someone who is arresting them. And there are fictional stories of vampires who bite, but of course these are not real people. Human beings are taught at a young age that biting is not an appropriate way to show anger or frustration; most kids stop biting because they acquire language and are able to express their emotions by using Words.
either they are Cannibals or they are human carnivores. GROSS!