If you think about the project as the people, then it becomes rather obvious that drive-by automatically generated patches don't actually contribute to the project. They are just so much noise. The people who generated and submitted them are not part of the project and usually don't intend to become part of the project. They didn't consult the other project members about their patches and they won't answer questions about them. They are like ephemeral ghosts, an illusion of contribution.