I suspect part of the issue is that dads no longer know how to open the bonnet, and thus never teach their kids.
Take tunnie's mates at work - whom I don't know at all, so making assumptions based on tunnie's age - I would wager none of them know how to do basic maintenance. I think as millennials go, tunnie is quite unusual in being able to do this.
In fact, taken a step further, as everyone knows, I work "in IT" (whatever the hell that means), and because my generation were playing on their Spectrums and C64s, I reckon in my office only a couple of people could do a basic service.
One of the convoy going over to France was a young, bright teenage lass who had not been driving long. As we got off the ferry in France, I noticed one tyre was way down on pressure and the 2 fronts were very borderline tread. So as I was putting air in (it was 18psi, car was fully loaded with 3 adults and luggage/booze for 10 days), I asked her what prep she had done. "Kissed the bonnet and tapped the steering wheel" was the reply.
I suspect that car, like so many others, gets a £99 "service"/MOT annually (ie, an oil change), and no other work.