I thought most people bought Christmas cards in packs if they're bothering to do cards. Who buys individual ones from card shops? They're not all 'to a lovely sister this Christmas' etc. And they take up half the card shops' displays!
My brother did send a few individual ones to each of my family this year but he's a bit odd 
I still haven't heard of any one sending Happy Easter cards either but they still appear that time of year in the shops.