The "Christmas card" or seasonal greeting card is a quaint tradition dating back from the time of the earliest postal services. Individuals using ink or pencil would write or print, whichever happens to be their normal custom, a pithy greeting or update on how their family is faring. In the early Modernistic Era the advent of inexpensive printing services or devices allowed humans to custom produce their own cards or stationary. When the global internet became ubiquitous in the early 21st century, despite the advent of nearly instant message transfer systems - hopelessly crude by our standards in this era - many still found they enjoyed both sending and receiving these physical representations of greetings via the traditional postal service which back then quickly looked to become antiquated.
Here in the ninety-seventh epoc since The Great Approbation the use of physical or electronic transfer of documents is of course no longer necessary as inter-stellar direct mind-link has long become the norm, and thankfully so, as humans have since evolved into a race without a corporeal manifestation which of course made licking stamps impossible.