The helicopter depends on a specific rotor geometry to fly. By putting the helicopter's weight on its rotors and bending them you risk severely damaging its mobility.
What's really neat linguistically is that "helicopter" isn't a compound of "heli" and "copter," but rather "helico" (as in helix, helical) and "pter" (as in pterodactyl).
"Rebracketing" is when this happens (i.e., the split in the word is moved in colloquial language).
Not 100% sure on this, but it may be due to 'helo' being more audibly distinct than 'heli' over a shitty garbled radio?
It could also be from different regional/national accents of English pronouncing helicopter as basically hee-lo-copter, sort of like how there are different pronunciations of Uranus or nuclear?
Heliskiing would be a lot more interesting if it was a fuel-efficient way to return the helicopter to the airport down in the valley after flying something up to the mountain.