Maybe we as human beings innately need a connection to nature. As our world becomes more industrialized and digital, we have been getting less opportunities to be out in the sunshine and enjoy the natural world. This is possibly why people go camping in the forest, swim at the beach, and hike up a mountain for recreation.
Maybe that's why my little one loves digging his feet (and sometimes hands) into the Earth's green carpet. I don't know for sure, but each time he plays is a beautiful reminder to me to pause and enjoy nature.