You'd Think We'd Have Figured It Out By Now

Jill overheard Grace talking to her friend the other day. Here is the conversation:
Friend "My baby sister had to have shots today."
Grace "Ohhh...that's sad! Is she ok?"
Friend "yeah."
Grace "I remember when I had to have my Kindergarten shots. I tried really hard not to cry. You know, I thought that those shots were going to make school easier. It didn't work."
Jill is trying her hardest not to burst out laughing at the disillusioned resignation in Grace's little voice. But she had tons of fun relating the story to me. "What the heck, mom? Didn't you explain it to her?"
I don't know. You'd think by the 4th kid I would have a clue about things. Just yesterday, I ask Grace if she wants cheese on her sandwich, and she said "Yuck! No! Cheese is made out of cows!" (Jill happened to be in the room then too...oh the eye rolling!) I told her, no it was made out of cows MILK, exactly what she eats with her cereal...and like the milk we shook to make butter a few weeks ago. Some milk is for cereal, some gets made into cheese, some into butter. "Ohhhhh!" she says.
Now this child is not dim. She's actually quite smart. But perhaps her mother just isn't doing a good job relating the world and her place in it to her!!!???? You'd Think We'd Have Figured It Out By Now.