Crack theory of the day:
Airbending is banned from pro bending because of the one time Tenzin substituted in on Lin's team when they were younger.
The opposing team had no idea how to handle him or his airbending, and no one could even land a single hit on him.
The judges knew they'd have to rewrite the entire rule book if he kept playing, so they just banned the element outright stating it was unfair as there were no other airbenders in the league to compete with him.
Tenzin was so angry about memorizing all the rules just to get banned forever, and that is why he calls pro bending "drivel" in canon. He is still salty about getting kicked out.













