I don't blame the ref that **** was getting to good to stop. Ref was like "naw **** that I wanna see how this ends."
I believe it is also a rule to prevent corruption. Back in "the day", the mob would pressure, or pay off a member in the fighters corner to stop the fight. Or the trainer or second could place a huge bet on his figher to lose...
But I would imagine that recommendation would be enough to stop the fight as the ref would be sued for recklessness.
'Only the referee can stop the fight' does not always apply. Some state commissions allow that the ring doc can stop it too. But in most cases, the rule is that the ring doc can only recommend to stop the fight, and the ref stops it then. The corner, or even the fighter himself, can not stop the fight, but as a golden rule the ref stops it when they quit/throw in the towel. In the Toney-Rahman rematch, Rahman quit by telling the doctor and the ref that he can't see and won't continue (after the doctor examined the cut and told him that it wasn't bad enough to stop the fight). At that, the ref stopped the fight and it was ruled a TKO victory for Toney. Two weeks later, the result was officially changed to a NC because the CSAC stated that the doc stopped the fight, and not the referee. However, according to the CSAC rules, the doctor cannot stop a fight, only the referee...