You bring up Vitali but consider that if the fight had gone further that cut potentially could have gotten much worse. See it's not always when a fighter is in trouble, it's when a fighter can no longer effectively defend themselv anymore. thats why fights are stopped on cuts because of the potential that it could

A) have a bad lasting result

b) worsen to the point where the fighter can no longer competently defend themself.

Its not just because the other fighter is hurt.