Why do you need full disk encryption in your day to day life? Are you a secret agent? I feel like that would give you our though.
It’s not a matter that I would have nothing to hide, this defense is stupid. It’s a matter that you should use a security adapted to your need, because the cost doesn’t offset the benefit otherwise. And with disk encryption you will far more often be sorry than happy if you’re a normal person.
People are imperfect. People have left laptops full of personal and/or commercially sensitive data on trains or planes, had them stolen from cars and houses etc. Full disc encryption is a defence against data breaches especially for computers that are not bolted down. Or it might be as simple as a person not wanting the embarrassment of their porn stash being found.