Play is THE way children learn and process the world around them. They're inherently driven towards it. It's how they integrate structures, boundaries, social dynamics, their own feelings and emotions, stressors and trauma, and changes in their world.
Children live in their bodies, which means they live in their "body and emotion" brain. This is why when our kids are having difficulty we see big shifts in their emotions and behavior.
Sometimes as parents we don't always know how to speak our kids language around play, emotions and behavior. Our own "play, expressive and creative" brain is tired and out of practice. We forget how to access that part, and use it to identify the internal struggles are kids are showing us.