Dos and don'ts on designing for accessibility (2016)
accessibility.blog.gov.uk
accessibility.blog.gov.uk
So yeah, best practices for disability accommodation are not just about handling the "<1%" (as someone in a different thread put it) that need them.
Unfortunately, the problem is most often not in applying the techniques, but convincing non-technical colleagues that these steps are important, even if they take a little longer.
Service designers, UX people and developers will take this user group into account at all stages of design, or else GDS won't let them GA the service.
Contrast it with the unicorn/more money than you can spend .com tech companies that view accessibility as a "necessity we wish would get away with" or small startups that view it as "why are you wasting your time with <1% of our users" and you see the challenges and design decisions being drastically different between different entities... :(
Bear in mind, accessibility concerns a huge array of people one way or another, from straight out being blind/deaf to dyschromatopsia and related issues, people unable to use a mouse etc... It's not an easy problem to tackle and it is a problem that I wish everyone developing for mobile/web would take into account every day...:/