Your brain is continually striving for predictability, and it can get pretty set in its ways. When a novelty appears, the dorsolateral prefrontal cortex (DLPFC) part of your brain is wired to review old rules and apply them to this new situation. It does not want to invent new ways if it can help it. This can hinder your creativity.
Combinatory play can help with quieting this part of the brain by relaxing your mind.