You know, we bring these flowers and put them on his grave, but they're not for him. He's dead, he doesn't need them. These flowers are for others, for people and society. We put them here to show that this person was important and we remember him, so there's some reason for him to be remembered. It shows that during life he did something great or important that people even nowadays are grateful for. Flowers are needed for others to notice and to remember. That's why we all come to graves.