That can definitely be a problem. But clearly you haven't worked with a codebase that decided that the best way to implement two (let's be honest: two if you're

That can definitely be a problem. But clearly you haven't worked with a codebase that decided that the best way to implement two (let's be honest: two if you're lucky, it could easily be 10) similar components is to duplicate the entire few thousands LoC. And then, when similar changes need to be implemented in both: to implement them in subtly different ways.