[asadotzler]

Accessibility issues are always usability issues if you're not a jerk who believes it's okay to not consider usability for about a quarter of the population.

Having said that, yes, tending to the needs of disabled people absolutely does help identify design shortcomings and making software better for disabled people often benefits far more users than than the targeted group. This is called the "curb cut effect" or simply "curb cuts" in the industry because like sidewalk curb cuts made for wheel chairs, the improvement was actually a win for everyone from jogger to parents with strollers, to rolling luggage, delivery people with hand trucks, etc. etc. When we make things better for one group, often many groups benefit so designing with everyone in mind, and not just people like you, is always worthwhile.