You may have heard several accessibility experts say that implementing accessibility can improve your rankings in Google, but the article SEO and Accessibility Overlap documents the different WCAG 2.0 requirements that also makes your site more Google friendly.
The reason for all this overlap? As author Liam McGee comments:
Google[bot] is blind. Googlebot doesn’t use a mouse. Googlebot sometimes has trouble with javascript. Like a blind person using screenreader software, Googlebot relies on structural cues in the content – denoting headings, paragraphs, lists and more – to make more sense of the page.
It just goes to show that you never know WHO could be visiting your Web site.