At a thread over at WebmastersWorld named Google Could Change the Web For the Better: If they could be bothered, the members discuss why Google does not give 'points' to sites that are fully accessibility in terms of Web standards.
A senior member says
Here is how I see it, get their own house in order (valid code, at least some level of accessibility) and then start to reward webmasters with valid and accessible websites. The vast majority would do it in a flash. Of course people would moan, so what, they moan when there is an update, they moan when their site is not #1, it would just be a little extra moaning :).
However, a post followed shortly stating Google is not out to police or enforce the the Web, "we are not the internet standards police".