Re: "Linux has had a fully functional development environment since day-1."?
If you're wondering around any medium or large-size project with vi, emacs, or ed then that way lies madness. You need to be able follow tags, get declarations, get call hierarchies, and so on. Split screen editors, compiler errors taking you to the right file in the editor, debugging using the editor windows, and SVN browsers are also extremely useful. That is why people like using IDEs.
Also, are people actually compiling on the Pi instead of using cross gcc?