I think the car issue is caused by rise of emissions controls. Efficiency and emissions control have been improved by computerizing the car - thats what puts car maintenance out of reach. Its hard for the average person to understand/fix things that we cannot see or touch.
I strongly suspect it's due to more than a single dimension. To name a few:
Emission controls, increased features (e.g. GPS, Seat warmers, lane assist), reduced fuel consumption, increased power, increased safety features, miniaturisation/lightening of components, reduced tolerances, materials specialization.
There are also more contentious but likely contributors, such as vendor lock-in (if you have to come to my dealer network form maintenance, I'm gonna make more money) or planned obsolescence (if you need a new car every X years, I'm gonna make more money).
