It’s surprising to me how many of my friends send Christmas cards, or holiday cards, including my atheist and secular friends.

Hitchens is remarking on the persistence of religious or quasi-religious customs even among people who explicitly reject religious belief. The surprise he expresses points to a theme common in his writing and speaking: that cultural habits, social conformity, and nostalgia often outlast (or substitute for) theological conviction. The observation also hints at a distinction between belief and practice—one can be secular in worldview yet still participate in rituals that function as social glue. In Hitchens’s framing, this can be read as a mild critique of unexamined tradition, but also as evidence of how deeply Christian-calendar observances have been normalized in Anglophone public life.