Because it doesn't feel like an extension, so it doesn't feel serious.
There's also a difference between knowing emacs and knowing emacs. One can use it proficiently for years and still be completely taken by surprise when starting up unassuming ielm and slowly realising you have the complete superbly documented system at your fingertips, followed--indeed--by wondering why not everything that needs a (text)interface is written in emacs.
You are quite correct, but it's not obvious from the outset.
There's also a difference between knowing emacs and knowing emacs. One can use it proficiently for years and still be completely taken by surprise when starting up unassuming ielm and slowly realising you have the complete superbly documented system at your fingertips, followed--indeed--by wondering why not everything that needs a (text)interface is written in emacs.
You are quite correct, but it's not obvious from the outset.