Accessibility is important, but somewhere along the way it got an undeserved reputation for being ugly, costly, and driven only by technical-compliance requirements. Making it an integral part of your design early creates something that is beautiful, inexpensive, and user-experience-driven. When someone with a disability comes across usability issues in your design, they're likely to be amplified. Something of minor inconvenience for a user could be a significant roadblock to another using assistive technology.