Well, it's just a natural progession of things, especially with CAFE Standards. Automakers are basically in a position to get as much power as possible from every last cubic inch of displacement. In the past two decades, they've really started getting creative with things like Variable Valve Timing, being able to run only 4 cylinders of a v8 car while at cruising speeds, better forced induction technology, etc. Engines have gotten crazy complex and the only way to make them work reliably is with the aid of computers. I think where the problem comes in though, is in recent years with the introduction of infotainment systems, all of the sudden there's a giant back door into the car. The computer that's used to run the car is no longer isolated, but exposed to radio signals and wireless networks. To be completely blunt, and I don't know if it's the case or not, but if car manufacturers aren't being careful with the security of the infotainment systems, they're being wildly irresponsible.
I think they're like industrial automation systems, people building them have been pretty isolated from most of the software world since before computer security was a big thing, so they haven't picked up the paranoia-but-in-a-good-way the rest of us have had to, and now they're not so isolated anymore and making the mistakes the rest of the world learned not to make in the 90s because they're only just starting to have to worry.
Overall, car design looks like a joke. A lot of crap ends up sticking, like not separating the starter battery from the rest of the electrical systems (compare: boats). In this case it's clearly not separating the CAN stuff from net enabled "smart car" crap