Is there any way to find out the motivation behind this? And who is responsible for this part of the legislation?
Motivation... I expect it's just another bullshit "law and order" law-enforcement power grab, thinly disguised as a "safety requirement".
If it is mandated that all cars should have this killswitch, then a lot of old-but-serviceable cars have to be taken off the road - and replaced with new ones.