A car, by now, is just a car. It's 2014, they are a known quantity, and the big change they were to bring, they have brought already.
Plus the key in the era of Mac and IBM PC was that the personal computer was just beginning and exploding from only nerds and large enterprises to billions of people. The personal computer was something genuinely new and disruptive for all kinds of markets, business processes and personal life. An electric car is just an incremental innovation on the car everybody already has.
Now, if it was a flying car, or a self driving car, that would have been more impressive in its possibility for change, but still nothing like a computer in the pre-mass computer era.
I have the same thought as you, what Tesla may accomplish as a company may not be affordable electric vehicles but leaps in battery and power storage.