A quick question to you clever rotary wing chappies
Clever? That's me out then.
I suspect it's down to the conscientiousness of the instructor when teaching airmanship and also some knowledge on the part of the instructor who may not, themselves, be aware of the problem.
Some of us have never flown in, let alone been at the controls, of a light fixed-wing aircraft and therefore may not be appreciate the difficulties concerned.
I was taught to avoid the planks and, with respect to the two main places from which I fly, we're kept a goodly distance apart anyway. Not everyone may be taught that as not everyone may be learning somewhere where the problem arises.
Maybe have a kindly chat with the local helicopter school if the aircraft came from that school.
Cheers
Whirls