So if you send a Christmas card to say 40 people, and (neighbours/colleagues etc,) and 3 don't send them back, would you send one again next year, and then the next year and the next???
Seems pointless to me, as they are not sending one for a reason; they either don't 'do' Christmas cards, or they don't particularly like you. (Maybe there are other reasons, I don't know....) So why keep sending one? 
My cousin keeps sending a neighbour of hers one (a woman around 50-ish who lives alone,) and complains CONSTANTLY that she doesn't send one back, saying 'it's very puzzling, I wonder if I have offended her, she seems ok normally!'
Personally, I would send a card, and if I didn't get one back, I would send another the following year. But if they didn't send one to me again, then I would not send one again, unless I got one first (as they are obviously not bothered about them...)
So AIBU to think it's daft to keep sending one when people don't send one back - ever (and then keep complaining that they never sent you one!
)