To receive funding from some government bodies in the US there is an accessibility requirement the funds recipient must attest. Of course they could attest to anything if they know the party they're making these statements has no mechanism to ensure the statements are valid.

Our best results in meeting accessibility has been to incorporate them into design standards guide and in a brand's style guide, right next to approved fonts, colors, logos, etc. Teams never think about asking for accessibility standards but always make sure to references the other guides.