It is simultaneously true that honesty is the best policy, but telling the truth is hard. Accepting a truth we don’t like is even worse.
For as much as people say they appreciate honesty, we know this isn’t always the case. Children are great at stating blunt facts and adults are quick to shush or scold them. We learn early on that honesty is not a universal constant, but something we employ with discretion
Like me, you’ve probably experienced times when your attempt at honesty went sideways, even if you were expressly asked for the truth. My ex often asked what I was thinking, but what he really wanted was for me to say what he wanted to hear. When your boss asks for honest feedback, diplomacy is the best approach.
In your fiction, your characters may keep secrets or they may try to avoid reality, even when it stares them in the face. But why? They, like us, know that honesty is preferable.
Their motivations may range from wanting to protect someone to wanting to avoid conflict or shame. They also may have had a negative experience with truth-telling.
A gay man may hesitate to come out to friends if he had a negative experience with someone in the past. An employee might not discuss personal problems if they think their boss will overlook them for projects or promotions. Someone may cover up abuse if they’d been punished for speaking up.
How have your characters experienced truth-telling? Did they learn to keep their mouths closed? Are they afraid a bad result will repeat itself? This can also apply to emotional change. A character who has lived through bad outcomes may hesitate to take a similar step.