JS,
It is not so much the air temperature but the water temp that creates the real hazard...as water is a much better remover of body heat than air.
Add in the wind to arrive at a chill factor and air temp can be an issue as well.
Now that the rigs are much further out in the GOM...and flying shuts down just a half hour before dark for single engined helicopters....one might be a very long way from help and thus be confronted with a survival situation that includes darkness, a bit of sea state, cold air and cold water....and if not in a raft...it could be a very cold night.
I will bet there are far more periods of time an exposure suit is needed than currently thought, if an honest review of the situation was done.
But then I love the comment...."statistically it is not worth equipping Pilots/Pax with suits!"