That's because they often see atheist as irredeemable, they think agnostic means being more convincable. Most theists I've talked to don't want to hear what I have to say and just like hearing themselves talk, especially when surrounded by others that share their beliefs. Perhaps they are conflating not actively believing in any deities with believing that there are none.

Come to think of it- no..

Mostly, they "listen" while formulating circular arguments. It isn't true interest in my thoughts as much as interest in converting my thinking to their brainwashed state.