Common Core was/is not about high-quality national education standards. It was/is not about getting low-income, high-achieving students into advanced math and science courses in high school and then into college. CCSSI was and is about how to lower the academic level of what states require for high school diplomas and for admission to public colleges.
It is incredibly important to reformers to be able to say things like "This teacher/school produced three more months of learning than that one." It is essentially the whole ball game. It is also pretty much a load of crap. But it is somewhat less bogus if you have the opportunity to authoritatively redefine the nature of learning on a year by year basis, limited to things that are relatively easily tested. That's the whole point of the Common Core, to tighten up and entrench their whole construct.