It doesn't unless the rider puts pressure on the steer's spine.
Bulldogging is a rodeo term for hanging onto a bull and hand riding it (riding "hands and knees") and remaining seated throughout. This technique was developed in order to avoid being bucked off by the bull, which can be dangerous or deadly because bulls often slam themselves down on their adversaries after throwing them off.
The Bulldogger might also grip the animal's neck with his left arm (if right-handed), leaving both hands free to use as he chooses; this strategy gives Bulldoggers more stability during grabs or faster efforts that would otherwise force their hands away from grabbing points on an unrideable animal...