Once something is totally digital eg. fly by wire, physics doesn't really hold anymore for the user where the computer is doing the work. Eg. the plane will go in any direction just by being pointed there.
And once you go off the edge of the world, the illusion collapses.
If you train people only inside the illusion, the first time they go off the edge into reality will quite possibly kill them - eg by a CFIT when the plane just doesn't have enough energy to clear an obstacle.
Exactly; See
Pinnacle 3701
Incidentally, the Pinnacle accident demonstrates that the problem is not unique to one nationality.