Honestly, as much as I agree on the need for an ideal buddy, the fact is that many spearos don't have it.
And the ones that have, often don't have it either.
How many of you can honestly say that you know 100% that your buddy is always spotting you, never losing sight of you in bad viz and never once going off after his own fish before checking you for a while after you surfaced? How many of you can honestly say that when that buddy takes a break, you don't do "just two dives more" cuz you feel great? Anything less than that vigilant a partner and the buddy system is an illusion, a fake sense of safety.
The perfect buddy, even for people who have buddies is a myth for the majority of divers.
Now, don't get me wrong. A half arsed buddy or even a great buddy is better than no buddy. Even the half arsed one might get lucky and spot you when you are in trouble. I would love a great one, would settle for a less than great one, but often I don't have any. And no matter what, I don't see how having an FRV can be seen as a bad thing, even in a buddy system. Unless it makes your buddy lower his guard.
Then comes the argument about diving safely and within our boundaries. Of course, that should be a no-brainer, but fact is enough good divers have BO'ed doing what they thought was safe. Doing dives of the same depth, time and exertion level that they have been doing for years. Not pushing majorly, just so happened that they were close to or did indeed BO on a what they thought was a regular dive.
It doesn't happen often, but it does happen. It's not like we have an LED read out of our fatigue levels on the dashboard in our brain. Anyone who really think they can read their bodies to perfection are probably kidding themselves.
My point is, we can do a lot to mitigate the risk, but it will always be there. I think we just take that very, very small risk because we love what we are doing. Human beings close their eyes to risk every day otherwise we would get nothing done.
I read plenty of people saying they'll get one when they have kids. Or divers thinking of getting one for their kid. I actually think that makes sense. You can play the (tiny) risks game with less implications when not that many people need you to get home every day.
I don't push myself on spearing ever and I am one of those guys, like all of us, kidding myself that I know where that limit is. I've done plenty 130 feet dives and static breathholds of + 5 mins but on spearing I don't do more than two mins and max 60-80 feet.
I still consider getting an FRV, it just better the odds even more. Can't hurt.