Besides avoiding Legal Exposure in the United States alone, your site may be inaccessible to.
Failure to comply with Section 508 of the Department of Justice ADA (American with Disabilities Act) Standards for Accessible Design could expose your company to hefty fines, the risk of expensive criminal and civil litigation as well as a reputation for being unfriendly to people with disabilities.
Websites who do not meet WCAG accessibility standards can be fined up to $50,000 for a first violation and $100,000 for a second, and even more for compensation of damages.