A few days back Roger Johansson contemplated the value of accessibility statements on web pages while, quit coincidentally, Accessify reader Rosie Sherry was having similar thoughts on the topic:
The use of web accessibility statements seems to be linked to the Code of Practice from the DDA . It appears that the fear of being sued over inaccessible websites led to the mass introduction of accessibility statements. This made it appear that people were making an effort to make accessible sites.
Word gets around easily on the web and this resulted in accessibility statements being implemented on many sites (probably around 12 million), usually copied and pasted from on site to another (as no official guidelines existed). The excuse was that they would help users, but time has proven that the actual practice of implementing accessibility statements has not gone according to plan.
You can read her thoughts here in the article Showing Web Accessibility Statements the Door