In this case, I’m not taking a big risk: everybody really does have something to hide. That’s just a fact And you do too: for instance, if some dude stopped you in the street and asked you your most intimate sexual fantasy, you wouldn’t readily tell them would you? Well there you go: you have something to hide.
I’ll tell you another story: a friend of mine had snapped holiday pictures of his family and put them up on his website some 20 years ago. One day, the fuzz knocked at his door, told him he hosted pictures of naked children, and arrested him on pedopornography charges - much to his wife’s dismay. The pictures in question were of his children on the beach. No matter how much they argued they were just innocuous holiday photos, that the kids were now grown up and willing to testify nothing dirty had happened to them in the past, he still had to spend a few hours at the precinct with the cuffs on, then hire a lawyer and fight the charges in court.
Well, 20 years ago, putting up photos of your children playing naked on the beach was okay. Today it is not. Things change, and stuff you think you have nothing to hide today may need to be hidden in the future. Like pictures of your kids. Or perhaps photos of your bar mitzvah if you lived in Germany in 1933. Or perhaps photos of you and your friends celebrating cinco de mayo if you lived in the US in 2020…
People who know history hide things that are perfectly okay today to future-proof their lives, and they don’t want to give out the decryption key. That’s also why encryption exists.