Ask Lemmy

First, because it protects otherwise vulnerable groups of people who fight for freedom and justice. Whistleblowers, journalists, independent intelligence groups need privacy to uncover the crime and abuse of the powerful without fearing repercussions.

Second, because being watched forcibly changes people's behavior. People are forced to be "normal", they do not allow themselves the same liberties they have when they're in private. When this becomes default, it negatively affects mental health, inducing severe stress and anxiety.

Third, because there are cultural conventions at the backbone of our society and the way it functions that are trampled by the invasion of privacy. You are taught to be uncomfortable when naked around others, to close off when you go to the toilet, to talk through your deeply personal or intimate matters exclusively with a select few etc. This isn't merely an isolated cultural quirk - it defines how we treat each other, how we communicate, how our sexuality and reproduction function (and who gets reproduced to begin with), how our relationships work, what kind of language we use, and more. Letting anyone or anything in just like that naturally makes many uncomfortable, and has the potential to be ultimately disastrous for the society we know - a kind of society built with expectation of privacy as one of its cornerstones.

Fourth, because the main groups that are interested in private information are governments (see the first point), those willing to manipulate you into buying something, denying your autonomy in the name of profit off your back, and those willing to manipulate your opinions, mainly political, to serve their interests.

Fifth, because private information is not always adequately safeguarded. Leaks can provide sensitive information used in fraud, blackmail, and by other malevolent actors.