There is another aspect too: when everything is in the stdlib it forces developers to collaborate and not create their Nth implementation of the same lib becaus

There is another aspect too: when everything is in the stdlib it forces developers to collaborate and not create their Nth implementation of the same lib because theirs is better. There is a breaking point in number of developers where it becomes more efficient to distribute the work trough a package manager but then you also introduce package hunting which can become quite a time consuming task.