Ask HN: Accessibility and How To Implement It?

After reading the "Don't Be Lazy, Use HTML Labels Correctly" comments, I thought I would attempt to further the discussion about web accessibility. My father is blind and one of the many reasons I'm interested in programming development, and the sort, is because I have seen how inaccessible many websites are. I have always wondered why that is, and after reading those comments, I am beginning to wonder where the HN community believes the problem lies. Is integrating accessibility limiting to your work? Is it the assistive technologies job? Is information on how to build accessibility into your frameworks hard to come across? Thoughts?