My first reason has to do with my Noni. As sketchy as this may sound, my entire life my Noni has told me never to put anything in writing. Once it's on paper, it can be used against you. I'm sure she was probably more referring to contracts or legal things like that, but her words have always stuck with me. Once I put my most private thoughts down on paper, they are free and in the world and can be used to hurt me. I always thought about the movies were the girls diaries are stolen and used to humiliate her in front of the whole school. I so did not want that to be me and the only way I knew of to ensure that never happened was to not keep a diary.
The second reason is something I've only recently discovered about myself. I am a very private person. I never knew! I thought I was open and willing to share all my deepest darkest secrets with everyone but its just not true. I love my secrets, I never talk about my deepest feelings, I protect my heart and give it to no one, I hate talking about anything intensely personal, and I try not to show too much real emotion. I honestly had no idea I was like this. I thought I just acted "strong" around my family because we have enough problems without me dumping my own on them, but I do it around everyone. I keep all those personal thoughts that people write in diaries in my head. I tried recently to write something meaningful in my little journal and I became acutely uncomfortable. So I would never keep a "real" diary because I could never write anything of importance in it.
Interesting stuff. This was inspired by my little journal, this blog, and the book series I've been reading, The Vampire Diaries, which obviously feature a lot of diary writing.