A child learns about the surrounding world through games. In my humble opinion, hide-and-seek is a symbol of the spontaneity that, as adults, we often lack in our complex emotional reality. Sometimes we all want to immerse ourselves and hide from the ordinary, look at the world with fresh eyes, turn everything upside down, and change our perspective.
By covering their eyes with their palms, a child feels like they have hidden and hopes that the adults will believe them and play along. Children can be sincere and naively good-natured.