Because it means breaking the rules of the game and affecting the player experience.

Tk circle is the acronym of team killer, which refers to some people who hurt their teammates maliciously, generally referring to those players who deliberately attack their teammates or other behaviors. People like them break the rules of the game and affect the experience of players, so when such people appear in the team, they are often disgusting.

Of course, this kind of behavior will also be severely punished by the system.