What HarrierDude says has some ring of truth to it, but truth be told with the exception of one or two EP's, there's nothing that's going to kill you immediately in helo (perfect example - there are no land immediately EPs in the Phrog).
His observation about breaking out is sort of true, but it actually is kind of easy to figure out who the good pilots are and who are shit. Coming from a community that's reputation rests almost solely on whether we drop a frag or not, that in nane systems knowledge comes in handy. Case in point - Quantico in Feb is cold, cold enough that after we started and got the rotors turning, our Tranny oil pressure is not within limits. Not even close. The needles' not moving. So we troubleshoot for a while and then it dawns on me that the pressure light is out (so the switch is working). Decide to taxi for takeoff - and by the time we hit the departure end, needle was on the move and we supported our Frag.
Other reason would be knowing just how far you can push a "Land as Soon as Possible" emergency.
That's about the only things I can think of.