Google has access to your current desires, things you say, search, email etc. Most of the information on twitter, LinkedIn etc is public unlike your private desires that only google knows from your search and ok google history
In fact, I would argue that Google has a much limited knowledge of our desires, opinions, etc. as compared to Facebook & Twitter. Yes, it tries to create a profile of who we are using the data that we provide to them while using their services. However, it is lame when you compare to the kind of detailed profile information that the other social services ask upfront, especially Facebook.