I'm surprised at how many posters have reported this tendency. I've been a daydreamer since as far back as I can remember, like to age 4. I thought I was unusual, but perhaps not.

My teacher in H.S. Driver's Ed noticed it and suggested I curb it behind the wheel. I spaced out, while waiting at a red light. When I failed to notice that the light turned green, he said, "Rose, what do you think about, while you're driving?" He sounded pretty annoyed.

I can become pretty oblivious to what's around me, if whatever is on my mind gets a hold of my attention.

I don't think my brain generates content, as well as it used to. Nowadays, I hate to be waiting somewhere without something to read. Used to be I could happily pass the time just attending to my inner world. I think boredom drove some of that mental activity, but not all.

Somewhere I read that daydreaming is a form of dissociation. That sounds right to me. It always did tend to make me somewhat absent to the reality around me. I wasn't escaping abuse, but I probably wasn't always getting my needs well met.