It's good to let people know you care, especially if they're not well. Sending a card let's them know that you're thinking of them, whether you're close by or far away, have seen them recently, or not been face to face in ages. A greeting card gives you the chance to write a few words and keep in touch, whilst also sending love and best wishes for a speedy recovery.
Whether the card recipient has had an operation, broken a limb, is suffering from a short or long-term illness, or is just having a few rough days, sending a get well soon card could put a smile on their face. The art work on these cards is beautiful too, so as well as your good wishes, the recipient gets a lovely card to put up in their room and look at.