No one has more questions than a 4-year old. It is a reflection of the child's development at this age and the way the child is experiencing the world. So what happens when the child grows older and goes to high school? We start evaluating the student with grades and pressuring them to succeed according to a rigid set of standards.
Is it any surprise that the student's curiosity about the world starts to shut down? As studies show, high school students ask about one question of substance per month in the classroom.
If the purpose of learning is to build the skills essential for future success, the way that we grade is neither a good indicator of that success or a good motivator to learn.