I Wonder Why Wednesday: Signing Casts

My daughter has recently gone through the process of breaking her arm, having it casted for 6 weeks, and now she's good as new. The first day I sent her off to school with it, she clutched a brand new Sharpie marker, so that her whole class could sign it. I'm wondering why we do this?

I know that we write well wishes, and get well soon's. Probably to cheer up the person who's stuck with the heavy thing for the next endless weeks. But, how did the practice start? In my breif internet search, I was able to find nothing.

My guess is that it started when Doctor's first started using casts for broken limbs and Mom's guilt kicked in, and she wrote "I love you sweetie, and I'll be thinking of you today, and I'm sorry that your arm is broken, and somehow, even though there is no reason for me to feel responsible, I am a Mom afterall, and I'm able to twist events so that I can somehow feel badly about not protecting you enough." Either that, or the kid got a huge goop on the pristine white cast, and Mom (smartly) wrote over it to make it seem like it was on purpose. Here's my daughter holding a dandelion curl.