That's not entirely true. org-mode is quite flexible and serves as a lot of things, and one of them is in fact as a TODO list [1]. This becomes particularly true when you use the TODO extensions.
I am constantly surprised at the capabilities of org-mode. Some sociologists that I'm aware of actually generate their LaTeX publications through org-mode [2].
I should clarify... Yes org-mode has todo features, including calendering, scheduling, etc, but listen some of the talks Carsten Dominik gives where he explains his rational: http://orgmode.org/talks.html It's core is as an flexible note-taking app with all those features as extensions to the core, just like the document links, and timestamp features.
In theory, org todos are born as notes which you later realize are actually todo items. Taken in this light, it makes sense as a text editor extension rather than an app in its own right.
I am constantly surprised at the capabilities of org-mode. Some sociologists that I'm aware of actually generate their LaTeX publications through org-mode [2].
[1] http://orgmode.org/manual/TODO-Items.html
[2] http://www.kieranhealy.org/files/misc/workflow-apps.pdf (generated through org-mode, source: https://github.com/kjhealy/workflow-paper)