Why do we wrap Christmas presents? We wrap them so the person receiving the gift doesn't know what it is. There's that element of surprise when someone opens a gift, not knowing what it might contain. A wrapped Christmas present is the great unknown.
Some people see this unknown as a challenge. They feel they must know what each present is before they unwrap them. They'll study the wrapped present. Feel it. Shake it. Squeeze it. Maybe even sniff it. To these people, no Christmas present is a successful Christmas present unless they know what it is before they unwrap it.
Not everyone likes to play that game, though. For me, Christmas is stressful enough without having to figure out how to hide presents, or wrap them creatively, or try to keep secrets from my wife. Once, early in my marriage, I made the mistake of telling my wife what a present was before I unwrapped it. We were rearranging the gifts under the tree and I picked up a present wrapped for me and said, "Oh, here's a pair of jeans for me." I wasn't really trying to guess what it was, I just picked it up and it was obvious, so I said it out loud.
It helps, too, that sometimes I'm not very bright. One year my wife got me the DVDs for the first nine seasons of the show Smallville. She wrapped each season separately, sometimes in different shaped boxes. And I was so dense that, even though I had already unwrapped Seasons 1-3 and Seasons 5-9, I was still surprised when I unwrapped Season 4. (My brother-in-law would not only have known he was getting all nine seasons, he would have correctly predicted which season was in which box.)
So, this Christmas I'm not worrying at all about figuring out what gifts I'm getting. I'll get what I get. And I'm also not worrying about trying to hide what I get for my wife from her. What I am worried about is trying to figure out what to get her. That's stressful enough.