Montessori observed that children become acquainted with the world through movement and experience. The process of making something instills an inner satisfaction in the child which he wants to share. By "doing it myself," the gift becomes a gift of the child's self.
That is one of the reasons we love making Birthday cards with the kids... it is an art project that turns into a one of a kind gift... even our 2 year old joins in the fun!!!
We start very simple, with white cardstock folded in two (or pre-made blank cards) We brainstorm about what the person receiving the card would enjoy best, since the main point is to let them realized that the gift is meant to make the other person happy (as opposed to just drawing what they like best). This also helps getting them out of the"artistic comfort zone" some children fall into - (rainbows and stick people anyone?)