drafts.

unpublished drafts are similar to unexpressed thoughts.

they may not be published due to several reasons.
the author might think that the writing is not ready yet to be published.
maybe due to its structure or unfinished writings, which ideas have yet to come to the author.
maybe the writing might offence or hurt someone else.
or maybe it is meant to stay as draft for the author to keep it to themselves.

for the latter,
personally, it is suffocating to keep something to myself.
it may not be appropriate to always express your thoughts to related person.
especially when it involves someone's habits, behaviour or beliefs.
*P.S.: when I say beliefs, it does not necessarily mean religion.*

as to avoid hurting someone else, I will write it instead and keep it as a draft.
I will review it over and over again, and thought to myself, will my writing hurt someone when they read it?

people respond differently to critics.
some may positively and think logically on why I have such thoughts.
but some may not.
they may misunderstood the meaning of a piece of writing, and negatively respond to the critics.