An attempt to answer the question at sports.inquirer.net. Not sure that there is a definitive answer to the question but the article does offer up some theories.
Parents and teachers around the globe are very proud when their children learn to play chess. They know it’s good for their kids. But why? Why is excellent chess instruction so beneficial to educational growth?
Let’s start with some basics. Kids do not get smarter when they’re forced to learn things that don’t interest them. They lose interest when they are not challenged. They also lose interest when they don’t understand what is being taught.
The best chess teachers are challenging and fun, while smoothly increasing the level of skill and understanding of each student. When teaching chess is approached that way, the kids remain interested and they improve. Studies done around the world prove that teaching chess to children has a very positive impact on their lives.
Regardless of the reason, chess is just a great game to learn. Start your kids early.