Why would pantheists pray? We don't believe there is a sentient entity listening who is capable of choosing to grant our wishes.
Prayer opens my heart. Normally, I go through the day trying to be functional and content. In prayer, I open my heart to my yearnings, and realize what I truly wish for, that what I wish for is not to get through my to do list, but for health and family and peaceful moments. In prayer, I wish well to people I care about, and to people unknown to me. Doing so opens up my compassion. I feel sadness for the hardships of others. When I open myself up to feel that sadness, I hopefully will be moved to act more kindly toward others. In prayer, I express my gratitude and joy for all the beauty that surrounds me, things that I otherwise might not pay attention to, things like friends, kindness, trees, and music.