Emacs comes with default settings. Some interesting features are disabled and hidden, i.e. ibuffer, Semantic, electric modes… Probably, to make it more user friendly to new users and make it behave more like "normal" editors, i.e. Normal users do not expect automatic pairing of punctuation marks like parentheses, brackets, curly brackets…

Because the nature of Emacs is an extensible system, people write extensions to improve Emacs and share with others. The extensions improve various aspects of Emacs: Improve existing and add new editing features, integrate 3rd party tools, add programming languages supports, change Emacs appearance… Without the ability to extend, Emacs will just be another obscure editor with some useful features but cannot meet the demands of people, because different people have different needs, and Emacs maintainers cannot provide them all and integrate all into Emacs. With the ability to extend, people can bend Emacs the way they want, much like Lisp.

Unlike other editors which encourage users to stay with the default as much as they can, Emacs encourages users to customize and extend Emacs as much as they can.