Gee, because it teaches nothing maybe….
Check it out:

Parents with school-aged children have a growing disdain for the Common Core State Standards, a new Rasmussen report found.

Just 34% of American Adults with children of elementary or secondary school age now favor requiring all schools nationwide to meet the same Common Core education standards. That’s an 18-point drop from 52% in early November of last year.

The Common Core website claimed it is a myth that “adopting common standards means bringing all states’ standards down to the lowest common denominator.” Parents and school teachers, however, are still incredulous. Principals in Hawaii even predicted a 30 percent drop in math and reading scores in the wake of the standards implementation.