accessibility toolbar buttons

I have a question – it’s not about anything not working, but about how best to use the plugin.

WP Accessibility includes options to show some “accessibility buttons” for things like high contrast view and greyscale. I realise that these are optional, I am just trying to figure out whether I should encourage or discourage my clients from adding these to their sites. While I can see that they might be handy to some users, they are not essential and you rarely see “accessibility buttons” these days, even on sites like RNIB with a large number of vision impaired visitors. Most people seem to think that you should just meet wcag guidelines and not bother with extra tools. I think the buttons are actually quite unobtrusive, but I worry that by giving in and letting clients enable them, (and even add ghastly text resize buttons!) I am not encouraging them in best practise. Just wondering if anyone felt similar or had an opinion.

https://wordpress.org/plugins/wp-accessibility/