hockey is probably the most inherently dangerous sport in the world, and the etiquette that keeps it from being a total car wreck has to be enforced. particularly in a sport where some enterprising coach could send out John Q Goonface to cheap shot a star without actually hurting his own team in the longrun

baseball has pitchers that will almost never have to stand in a batters box and face the music if they decide to throw at someone, and getting kicked out of 1 of 162 games isnt really that big of a deal.

football punishes its violations in ways that preclude someone from having to throw hands on behalf of their QB or something. same with basketball, in that dangerous plays are generally punished in ways that keep situations from escalating.