I [think because I live a boring, uneventful life and there's no possible way I could be hauled in on trumped-up or false charges, because that never happens ever, that no one else should have any privacy either.
If you don't understand or value your rights, that's your own shortcoming. Not valuing others rights and arguing against them makes you a threat to them. Try life in China for a while to see how much you love having to censor your words for fear of having someone other than he intended recipient read and object to something you wrote, take something out of context, or even simply not "get" the sarcasm/wit/humor of your private correspondence. "But our justice system is infallible, and it never ruins people's innocent peoples lives..." Look into it, even once. That's what you're putting your trust in; other very fallible people, with a horrible track record of ineptitude, inaccuracy, politics and abuses.
We've got a Supreme Court Justice unelected & granted with absolute power, talking about how not just opening the floodgates to buying congressional votes, but even discussing campaign finance reform at all is anti-American and a potentially punishable treasonous offense. Treason still punishable by hanging. The DOJ has overtly cleared the way for a return to prosecutable thought-crimes again. Hell you can now be convicted for speaking critically of certain high-donating actively lobbying industries and even individual companies. Etc. etc. etc. Thousands of these anti-citizen, pro-consolidation of power/money laws rammed through, and thousands more scheduled. No country has seen such a radical loss & reversal of their liberties without descending into civil war over it.
If after the last 70 years, you still think the FBI, CIA, & now NSA think of you as anything more than an inmate awaiting your conviction, you need to start paying attention, because they make no bones about it. You don't even need to go to the conspiracy theorists for the horrorshow, you can just listen to Congress and the Supreme Court in their own words.