One of the hardest things to wrap my own head around as a new parent was that the kid was going to forget all this stuff anyway. All these milestones, exciting moments, encounters, activities, all of it, would be gone by the time she was like, 4 or 5.
It's called Childhood Amnesia, or Infantile Amnesia, and it's believed to have to do with the way the kid's brain, self, and/or language develops.
Of course, that doesn't mean you're off the hook, or that whatever happens to a kid from 0-5yo doesn't matter. Just the opposite; you do it for the development. For the moment, not the memories. There's a phase in a kid's life where the parents have to be the ones storing the memories, which you can relay later as embarrassing stories.
Metafilter recently hosted a long, fascinating thread where people started sharing their earliest memories, and discussing things I'd never considered, such as the blessing of being able to forget an abusive or horrible childhood.
Childhood Amnesia [metafilter]