Why education systems around the globe have been slow to adopt Computer Science (CS) in education?

Technology becoming almost omnipresent, a lot of studies indicates that CS is important to combine with current learning model to strengthen the existing education system. Computer Science (CS) is rising attention and expanding as more and more national education systems recognize its importance. However, the report:What do we know about the expansion of K-12 computer science education? A review of the evidence shows that the integration of computer science by education systems around the globe have been slow to adopt CS education. What are the challenges to implement CS?