This is actually a really interesting question and made me think since a couple of the races I've done recently, I've witnessed boats go over all around me.
I think I've established that in most of the races I do, all boats are required to carry a VHF. Without realizing it, this has made me feel if I didn't hear a call on the VHF, all was well and the overturned boat was managing on their own.
After this weekend, this still makes sense except for one thing. I discovered my VHF was not carrying more than a 3 or 4 miles. When I tried to notify the RC that we were retiring, I could not get through. This made me think, if things had gone the other way and we had a very serious emergency, I may not have been able to summon assistance.
We are racing high performance boats where wipeouts are common. The real question is when is it serious and how do we know? My own common logic has always been to err on the side of caution, but clearly I have not always followed this rule when I've seen overturned boats. I think this is a great debate that should be discussed.
TB