But having that tracking shown to you has a very powerful psychological effect.
It's pretty well established that increasing penalties for crimes does next to nothing to prevent those crimes. But what does reduce crime rates is showing how people were caught for crimes, making people believe that they are less likely to 'get away with it'.
Being confronted with your own searches is an immediate reminder that the searcher is doing something illegal, and that they are not doing so unnoticed. That's wildly different than abstractly knowing that you're probably being tracked somewhere by somebody among billions of other people.
I mean, I know Google has been shitty lately, but Wikipedia isn't hard to find: https://en.m.wikipedia.org/wiki/Deterrence_(penology)
I'd wager Nintendo has put some fear into a few folks considering developing emulators, but that's the only comparison to be made here. The lack of any real consequences for individuals downloading roms is why so many are happy to publicly proclaim their piracy.
Now, I bet if megaupload added an AI that checked users uploads for copyrighted titles and gave everyone trying to upload them a warning about possible jail time, we'd see a hell of a lot less roms and movies on mega.