Personalized baby calling cards

I recently had a custom request to create baby calling cards to match my existing seersucker stationery set and onesie stickers. Here's how they turned out...

 

To be honest, I never really thought to include calling cards in my shop. And now I feel silly, being a mama AND a designer, I've never used them myself, so didn't know how "popular" they really were/are. Thoughts? Any moms out there lovin' on baby calling cards? Any of you not have a clue what you'd even need them for... to send as thank you notes, use as play date scheduling cards, add your contact info and use as mommy "business" cards, gift tags and more!