I think they’re broadly pointless. I got out of the habit a few years ago when I found myself stuck in the loop of sending cards to everyone I’ve ever met ever. People at work give a card to all their colleagues, sweet gesture and all but *I see you five days a week*. I had a bit of an epiphany and decided I wasn’t doing it any more, the only people who benefit are the Royal Mail (who have enough to do right now) and card manufacturers.
So I don’t send cards any more if I can help it, other than to people who I want to send a personal message to (OH, mother) or people I’ve not seen in a long time.
If I get cards I don’t mind, but I’m really not fussed either way.