I'm not generally the card giving type, but I agree that it feels nice to receive a card sometimes. Even if the sentiment is generic or unoriginal, it does feel nice to know that someone is thinking of me. Sometimes, the sender may choose generic, because they truly don't know what to say (I can think of sympathy cards for instance). Sure, I can think of things that a person may want to write, but I don't judge the unoriginal.
In my family, though, it is sort of a joke. You may receive a recycled birthday card with the previous sender's name crossed out and replaced with a new name. It's all in fun, of course, and no one seems to mind.