What makes you think there's an opt-out with Google? I never opt-in or use their email, photos, etc., but can't seem to keep their cookies off of my machine for more than a few seconds.
At least with the government there's some representation! I have some control, however small, and the government isn't going to be interested in me since I'm not a criminal or terrorist. Google's interest in me is unending and insatiable.
First, Google cookies track a unique identifier that they generate for you across multiple websites. Over time, it is certainly possible to link this identifier to an individual identity, but generally they don't care. Advertisers just care about your characteristics and habits, not your name (ex. they care that id 1234 visited uhaul.com within the past 30 days to offer ads of moving companies, they don't care that id 1234 is James). Also, this unique identifier can be reset whenever you want, and starts the profile from a clean slate. Further, there is nothing wrong with using adblockers which are quite effective at blocking these sorts of tracking cookies. I use adgaurd, and it constantly blocks googles tracking cookies. While this isn't a perfect opt-out, it is still an opt-out of sorts. I can choose and control what data my computer accepts or rejects. An even more extreme would be to simply block all cookies.
Second, I think it is naive to assume the government isn't interested in you on the premise that you're not a criminal or terrorist. There are lots of criminal laws - unless you have memorized them all and take great care to avoid them, odds are you've broken a crime or two. It's likely deminimus, but a crime nonetheless. Inchoate crimes are particularly difficult to avoid. If a government collects a database of every instance everyone has committed a crime, no matter how minor, and the the government has the power to choose whether to prosecute it or not, the legislative and executive branches are essentially merged; the government can choose to haul anyone in for anything they want when it's convenient. This is of course extreme, but it highlights that there is a reason some rules exist only for the purpose of frustrating the government's ability to find crimes incentivizes the inefficient procedure of due process (4th Amendment and the Exclusionary Rule, for example). There are no similar rules under the Patriot Act - indeed it seems to be all about avoiding that pesky due process.
I can block Google cookies easily. As far as know, I'm not a criminal or terrorist either. But I'm sure some drunken texts or joke emails between friends could the linked together to form a basis to prosecute us for conspiracy or solicitation or something. Right now the government wouldn't bother. But in the future, who knows what their interest will be? The US government wasn't above that in 1942, that was pretty recent.