To increase the coupling between primary and secondary, thereby increasing what I've been calling 'effectiveness' (of energy transformer). Again, if you think that there would be lots of 'losses' (poor efficiency) in the absence of a core, where do you think that the 'lost energy' would then be dissipated?
Absolutely my last post in this subject, as we do seem to be going around in circles....
The losses with be in warming the air, and assuming the vehicle has a metal chassis, in warming the chassis.