While I was working in the US I was almost never pushed to consider accessibility. It just wasn’t talked about or (it seemed) even considered during the design process but then I moved over to the UK and all of a sudden I had to know it. I had to know what worked and what didn’t.
But why consider it? Bottom line if a site doesn’t work then that’s simply bad form. It is also the law both in the UK and US as well as many other countries.
That 11% translates into millions of people who will not be able to access your site and if you are a company who uses calendars for picking dates such as the case of Sky Broadband in the UK when users are choosing dates for broadband connectivity then you are risking losing millions of potential customers. Or in the case of a travel site which doesn’t downgrade to a text based version then those users will not be using your site to book travel. If your site makes money on advertising then you will lose revenue because those users will simply stop using your site. Over time that translates to millions of dollars/pounds in lost revenue.