Re: "A direct causal link is difficult..."
There was a dramatic rise in BMW thefts around 2011 - when thieves found they could just plug into port in car and program car to accept another key, compounded by a flaw where if you jammed a screwdriver in drivers door and twisted hard you could make it wind down window. There was a long running thread on Pistonheads about it - link, I believe other makes flaws were attacked later
Now they can make some with "comfort access" just unlock and start with a pair of extenders - link
Then there is the lower tech style attacks - just leave a jammer around which will stop car locking