There's an eternal debate over what the real purpose of Hearth's Warming is: giving gifts, reconnecting with family, remembering the Fire of Friendship, and dozens of other interpretations. It's not a dire question, and many ponies don't give a second thought about their answer.
Rarity, however, did.
If Cadance is willing to listen, she's willing to share.
Written as part of The Incredible Amazeballs Jinglemas Secret Santa Compilation. Go read everything else there, even if you don't like this story. Seriously, it's got people like shortskirtsandexplosions and KitsuneRisu in it: it's high-quality stuff.