One of the reasons people may not disclose more about themselves is for fear of being judged. The threat of negative evaluation from others–such as being negatively perceived by your date–is the root of social anxiety, and is exacerbated in a dating setting.

Why do I have so much anxiety about going on a date?

Anxiety often occurs in a cycle. When were faced with a trigger (such as going on a date), we cope with our overwhelming feelings by avoiding the trigger (bailing on the date or avoiding having dates set up in the first place).