Well compare to mathematics for example, you could wait until kids are good at using a pencil and paper to start teaching them mathematics. But there's really no need, with modern iPad apps you can teach addition, subtraction, multiplication and some of the associated reasoning skills before kids have the motor skills to be able to write numerals well. Do they need to learn math this early? I don't know, why not try? If you can get kids to like learning things then why not.