WordPress Tavern makes a case for why accessibility matters in WordPress. In the meantime some of us have been discussing this for 25 years, and so have something to say about it.
The main problem with accessibility is the term itself. What we are actually talking about here is a universal user experience.
The industry needs to stop selling accessibility as a checkbox and we need to stop viewing it as something extra to do. Inherently every feature and decision we make is already more or less accessible — it is not an on/off switch.
By applying the inversion principle, we should look at what barriers are preventing people from using our websites to the fullest extend, and code all future solutions with these lessons learned.
Aiming for anything less than universal access also makes little economic sense. Let’s ask ourselves: why make a theme and then make it hard to use on purpose? Why make a theme and only allow a subset of people to use it? Do you only allow people with a first name in the first half of the alphabet to log in to your site? Let’s not artificially limit the versatility of the web.
A universal experience should be expected now, and when someone cannot use your site it is a bug. Your site is not inclusive when people cannot use it.