Just to be clear, I agree with you that STV would be an improvment over the current FPTP system. Regarding why people feel they need to understand how it works, I can only speculate. First of all, reforming an electoral system is of much greater consequence than, say, deciding to get the automatic transmission package or anti-lock brakes (to continue with your analogy) and harder to reverse. That combined with a general mistrust of politicians and whatever particular Kool-Aid du jour they happen to be pushing. Add to that the usual inertia that must be overcome to get people to want to change. If they haven't been sold on the idea, any excuse will do not to support the change. Thats my guess. Final answer.
Along my last point, personally I am disgusted (but not surprised) by the lack of thoughtful discourse on STV. I.e.What it is, what the beneifts are, how will this change the power balance, what the potential drawbacks are etc. Just the usual partisan FUD throwing (Fear, Uncertainty and Doubt).