I'm with Weldo.
Accessibility and usability should be ensured on every website, law or no law. It's just laziness or ignorance. It's not very hard to develop a website that can be "viewed" (for lack of a better word) on any browser, or screen-reader, any platform.
Making a good looking website does not make a good web designer, making a website that meets a specification does. That specification is to be accessible by anyone. When a company hires you to develop an e-commerce site they expect 100% of web users to be able to access it. If you base your thinking on the fact that you can afford for 2% of web users to miss out, then you might as well disregard screen resolution, connection speed, and web standards all together.
After all, it's good practice and it does improve your search ranking. Just do it.