Scale.
40, or even 20 years ago, the State might have been able to note a record of phone calls, postal correspondence (look up "postal covers"), some financial purchases, periodicals subscriptions, and with a great deal of effort, some of my travels and movements, mostly limited to specific port entries and exits, and air travel.
But unavailable would have been: dictionary queries, encyclopedia queries, books read, specific magazine articles read, the contents of virtually all conversations, detailed movement and location history, social associations, detailed purchase history, and more.
Today, mobile devices report location to a precision of inches at a frequency of minutes. Any random query of momentary interest can create a permanent record. As a HN submission earlier today notes, simply casually perusing a document -- clicking a link -- can result in having your home raided and all electronic devices confiscated and held for a year: https://news.ycombinator.com/item?id=21992491
The scope and scale of intrusiveness is absolutely unprecedented.
Yes, the State has some rights and powers. It also has a tremendous responsibility, which it increasingly seems to fail to excercise appropriately.
And I say this regardless of specific country or jurisdiction -- the story linked above comes from Germany, and instances readily come to mind from the UK, US, Japan, China, Russia, India, Saudi Arabia, and elsewhere.
The corruption of absolute power is not bounded by culture, constitution, or ideology.