RoboCup is arranged with the intention to use RoboCup as a vehicle to promote robotics and AI research, by offering a publicly appealing, but formidable challenge. One of the effective ways to promote science and engineering research is to set a challenging long term goal. When the accomplishment of such a goal has significant social impact, it is called a grand challenge project. Building a robot that plays soccer will not by itself generate significant social and economic impact, but the accomplishment will certainly be considered a major achievement for the field. RoboCup is a landmark project as well as a standard problem.
For more information, visit the RoboCup website