Sure, it would be some extra work for Apple, but that doesn't mean that it's not the right thing to do for consumers. Apple created the ecosystem and their own rules where most people follow along, but that doesn't mean it couldn't be better or that it's exactly mostly in consumer's interests. I agree that it wouldn't really be done and all that, but that doesn't necessarily make it all that right.Fair analogy, but not quite the same thing. Apple would have to go out of their way to fork iOS 6 on iOS 7-compatible devices, whereas merely replacing the horn would be much simpler for the car manufacturer. There is no real reason why the car manufacturer would need to replace more than just the horn, while Apple has a good reason to not spend time on releasing another update for iOS- the fix is already available on a newer version. You could say that it would be as simple as taking the already released iOS 6.1.6 and making it available for devices that have not been updated to iOS 7, but it would have to be tailored and tested for each device just like any other version of iOS. Apple likely sees no need to go through that effort, and that mentality isn't going to change. The vast majority of customers are happy with iOS 7, and it's not worth spending time and effort to please a small minority that likely isn't going to be pleased no matter what Apple does.
(If you think about it, for years Apple never allowed users to even do anything about the automatically downloaded updates onto their phones, until iOS 7.1 where they finally provided that option, interestingly enough it just happened to coincide with more uproar about it in relation to the iOS 7.0 update and even actual class action lawsuits being in the works in relation to it. So clearly the way Apple was going about it wasn't exactly the best/right way given that they did end up changing it finally, thankfully.)