When the incisors are unlevel they force the teeth apart as the horse chews. Certainly, any horse with severe abnormalities of the incisors could benefit by having this done. They grow in just in front of the large cheek teeth. Many are probably no problem at all. If too far forward the bit can come into contact and may become sensitive or interfere with the action of the bit.
All young horses have problems with their bits from time to time, greatly confusing the subject.
On a young horse with biting problems removal may help. Also tremendous plaque build up around the molars can occur in horses that quid. Allowing the plaque to eat away at the gingiva results in premature tooth loss.