What seems like an innocent conversation to you may actually be a touchy subject for me. It's hard for me to talk about some things, but I am willing to go there if the conversation warrants it and we are bonding or whatever. I am not willing, however, to bring up all that shit simply because someone is curious or nosy. In discussions of a personal nature, things just have to flow.
For mundane things, it just amazes me why you need to know in the first place. How does what cereal I ate affect your life? If something is nonsensical to me, I react to it very poorly.