Lefties and righties is just a convention case, if humans had three arms, two on the right, there might have been a matter of fact as to coming from which arm preference things go better.

Sure, but there are cases where rivals are evenly matched. Lions and tigers, for instance, have different - often conflicting - aims. However, it isn't a walk-over for one team. Of course, you could say whether the lion or tiger genes win is "just a convention" - but to the lions and tigers, it really matters.

To begin with, on the limit, if you value A B and C intrinsically but you have to do D1 D2 and D3 instrumentally, you may initially think of doing D1 D2 and D3. but what use would it be to fill up your future with that instrumental stuff if you nearly never get A B an C [?]

No use. However, our values are not that far from Universal Instrumental Values - because we were built by a process involving a lot of natural selection.

Our choice is more like: do we give up a few of the things we value now - or run the risk of losing many more of them in the future. That leads to the question of how big the risk is - and that turns out to be a tricky issue.