Does it? Try Googling from an incognito window on your neighbour's wifi. Use a live distro if you want to be completely sure. Are the results significantly different? Are ads any worse?
I have tried a couple of tests like that (on other people's devices, etc) and the only noticeable use of that trove of data Google has about me is suggested searches from my search history. Google Now can also pull an article of interest every once in a while the same way.
That doesn't mean they don't have the data and won't cough it up on government's request but there seems to be very little effective mining going on.