It's a tradeoff, if you really believe that the government are motivated solely for your protection then of course you would allow them unlimited access into your personal life (as long as it was invisible to you, via your phone/computer, why would you care? They only use that information to help you. Think Doctor and seeing you naked, you trust that they don't care about seeing you naked, they just want to help you.)
If you're the director of the CIA maybe you really believe that the government having unlimited invasion of privacy is the correct way to keep everyone safe.
2) Control. This level of surveillance is key in the primary purpose of dissident control. This is why they are harping so much on "lone-wolf radicals" who are "radicalised by the internet". Because they want to say wolf so loud and so much that nobody has the chance to remind them about the constitution. This is also part of why you will see a huge increase in bad legislation written and passed by corrupted good ol boy house/senate. The internet is a threat to the global order due to it's decentralized nature and it's encouragement of anarchistic freedom of thought. The oligarchy are moving against the internet.
3) Fall-guys. The more sinister, grander chessboard for the supranational oligarchs is one of de-legitimizing American power and principles. I'll let you digest the details of this.
Always remember where the Company got it's start. Wall Street international lawyers. I'm pretty sure McCarthy, despite his unconstitutional antics, was actually on to something... but he just didn't aim high-enough in the chain. Corruption in the three-letters is top down.
http://www.maebrussell.com/Prouty/Harry%20Truman%27s%20CIA%2...
Now we could argue if the CIA works for the well being of the majority of US citizens, or to defend the obscure interests of some minority. And discuss the historical role of the CIA "fighting terrorism".
There are also the conspiracy type reasons but I think it's just a jobs program for white upper middle class men.
Also, the current obsession with machine learning is amplifying the problem. It's easy to misuse data analysis (e.g. overfitting the model until it says what you want it to say). Data is seen as valuable on it's own even if it isn't useful "now". This produces an effect similar to tulip-mania where everybody wants as much data as possible even if it isn't currently useful.
Finally, add in bad incentives where failure is rewarded with more contracts. As Mudge (Peiter Zatko) gave a very good description[1] of this problem which he called "game theory is a bitch". The solution is to make retaining data toxic with liability.
If massive financial fraud, corruption and widening inequality continue to get worse, there is going to be a lot of unrest in the western developed nations.
There's only so much shit people can take, so much of their shit that can be taken from them before they realise their entire financial system and wars waged are a giant ponzi scheme set up to suck resources from the many up to the few.
This shit happens in cycles. The upper echelons of society know this is coming again.
Well, combine that with knowing almost everything about everybody, and you can use the threat of charges or actually having them charged to deal with dissidents.
I once knew a gun rights' activist in the US. He has friends who were targeted this way by the Federal gov't. It's not just a theoretical thing.
From the logo of the former Information Awareness Office (under the pyramid-with-eye, of course):
scientia est potentia