Accessibility is the science of developing technologies and interfaces in such a way that users with limited abilities (visual, auditory or control impairments) can use tools and channels to achieve parity with those whose abilities are not. Web pages separate text from the interface and the design, so that screen readers can read out text to those who cannot read. Assistive input devices like sip & puff devices and wands allow input without keyboards.
You would ask me, why go to such extremes of building assistive technology and capabilities into what is ultimately a short lived campaign? Our budgets and timelines would never allow for it.