It doesn't matter to me if it is because a screenreader, a Lynx browser, a preference, or a no-script plug-in. All that matters to me is my users can access my content on a broad range of devices.
CSS on/Images off is an unlikely scenario, but it is a possible scenario (also consider the possibility of images not loading for whatever reason). If I were a user stuck in that scenario, I'd say: "I can't access core parts of this website". For a website developer, you could call that an accessibility problem, no?
Relevant thread on WebAIM: http://webaim.org/discussion/mail_thread?thread=3785 A little more cheeky: http://www.arespritesaccessible.net/explain.php Wikipedia: Web accessibility refers to the inclusive practice of making websites usable by people of all abilities and disabilities.