[10ren]

Great question, thought-provoking answer.

Similar to what the article says, I think constraints can engage us more, by making our decisions more meaningful. We have "If we do X, it will overcome that constraint! How cool!", instead of "I guess we could do X."

I thought the article was going to say that constraints make the problem more concrete, and it's often easier to think about something concrete than something abstract. It's easier to grasp, easier to relate to existing knowledge and previous solutions, and it tends to engage our unconscious more, which is where creativity (apparently) resides.