If 3rd party cable can do exactly the same but cheaper, why not? Consumers like us drive production efficiencies and forces companies to work towards driving down cost. That's how consumerism drive the market. My money can be better spend on more value items. Since first generation iPhone, I had no problems using 3rd party cables and cheap at that as well.
Why not just use apple earbuds? Why pay $$$ for other earbuds? Are apple earbuds the only one we need to use? There are cheaper earbuds out there with better acoustic performances than the old apple ear phone that came bundled with the phone.
Your example of jaguar is not really similar. Parking and petrol are not accessories.
Well, this kind of explanation I have heard aplenty of, among those I know.
All it takes is just 1 incident. Eg. cable heats up and emit smoke, or even in a worst case scenario, short circuit the iPhone.
Above has happened to a friend who used to say the same damn thing until that 1 incident.
Anyway, it's individual's choice.