kudos - great idea! People who are not disabled may not understand the need for this why do I need this? how this could have an effect on my site (positively)?

kudos - great idea! People who are not disabled may not understand the need for this why do I need this? how this could have an effect on my site (positively)? it would be great to show a casestudy - how you transformed an inaccessible site to an accessible one.