Glad you asked that. Most people don’t realize that dogs have scent glands in their paws. Kicking the grass or dirt or whatever happens to be around after relieving ourselves is our way of “spreading our scent” and “marking our territory.” It’s also a way of showing dominance.
I’ve been doing this behavior a lot lately to show that I really do rule the world. This is my way of showing it, a little bit at a time. Someday everyone will realize that I am the queen of the Universe and they shall obey me.