1) The Waiting School believes that the anticipation of opening the box makes the contents that much better, gives them more time to age, and most importantly, gives the user the excuse to keep posting in the thread.
2) The Open Now School believes the gift should be recieved as such, and the sender enjoys seeing your reaction as much as you enjoying finding out whats in the box. These people also have no self control.
3) Mike's Theory of Secret Santa Gifting is that since 'Christmas' may mean different things to different people, everyday could be Christmas. Therefore you are waiting until Christmas to open your package whenever you choose to open it.