when it is in the dark with no lighting except the landing lamp and you are not practised in the technique.
It is fine if you are on instruments as you rotate but if your IF ability is poor and you are trying to look outside instead of inside, there is every chance you will hit the ground/sea.
Ask anyone with experience of night deck departures from a ship where you go from some external references to none at all just as you transition.
5 years RCAF Sea King at sea and 15 years of SAR here.
Been there, etc.