Most people don't have the resources, knowledge, or desire to replace their car's engine parts. Does that mean it's ok to sell a car with a locked hood, that requires a manufacturer-controlled key before the engine can be serviced?

No, even if they personally don't want to touch the engine, they turn to knowledgeable friends/family or pay a professional mechanic to do the work.

This unfortunately-common view that most people should never even have the option to do anything technical is insulting and maybe even monopolistic (it bans 3rd party repairs/parts).