Mmmm we all participate in decisions which are only opinion, i.e. morals where we talk about truths, and in terms of social norms we are forced to act as if we believe things are truths. To be honest, I see a lot of the use or misuse of agnostic language to be a sort of learned sop to avoid a burden of proof.
On an intellectual level, I accept the possibilities of many things I have no belief in, but in a day to day approach, and use of language, I approach them as truths.