Some (WP) agencies are really into accessibility. However, when you do support accessibility as a developer, but not really pay close attention, there is a big chance you are unknowingly building inaccessible Wordpress websites for your clients.
Knowledge and cases
Accessibility is like privacy: it often isn't the core business of a company. Even menu's become the victim. As a result, some might never be able to reach or interact with your main navigation.
Being a recommendation since June 5th, 2018, the Web Content Accessibility Guidelines 2.1 got translated to Dutch and published by Accessibility Foundation.
Last monday, I visited Wehkamp. They boosted the pagespeed of their productpages after taking part in a Google Speed Race and ending up second.