This shows you either didn't read what you replied to or don't understand the subject.
This file is the public interface of the Linux system to everyone who wants to get information about users on the system. It doesn't matter that alternative tools exist: they were already mentioned in the post you replied to. It's not the point...
If I didn't understand I'd be grateful if you could explain it.
As far as I know that file does not get referenced for the users in an external directory server. That's how the systems scale without needing to put the users in the file. Aren't we talking about a high number of users (and their authorization levels) when talking about scalibility in this case?
This file is the public interface of the Linux system to everyone who wants to get information about users on the system. It doesn't matter that alternative tools exist: they were already mentioned in the post you replied to. It's not the point...