What additional information do you think Google has available about its users that they are not showing?
I'm not necessarily saying that this data is already compiled somewhere - but Google being a data-oriented company, they could most likely do all this if they really wanted to.
http://www.google.com/s2/search/social
https://www.google.com/settings/ads/onweb/
(not sure the links work, you get there through the dashboard)
In other words given all their options and incentive they don't seem to get any benefits from really exposing all the data they have about you. One can argue that is really they most precious resource.
They have some incentive to expose some to make you feel like you are somewhat in control and they are somewhat open and transparent.