Calvin and Hobbes was a massive part of my youth. It fed that creative and mischievous part of me that "regular" life just wasn't satisfying. I was smitten and still am.
Fast forward to my daughter's birth... At around 4 years old, I bought her the giant anthology of strips which includes everything Calvin and Hobbes ever printed. Like me, it shaped her in undefinable ways. It drove her drawing and reading off the charts. She very much grew as a person because of Bill's work and my influence in reading to her often. She took over very quickly! She latched on and studied those books with a fervor that I've not seen repeated in her yet.
Do you think the result would have been the same if there were T-shirts, TV shows, video games, and the like plastered all over? You can only shield a child from the world so much. They absorb everything.
Anyway, I think Bill absolutely made a most excellent decision. Not only for himself, but for us.