Only the worst teachers failed to motivate math procedures. Granted, the curve may have been skewed to worst. :) But CCSS does not suggest a little professional development to get teachers to explain the "why" behind the procedures, it wants kids to invest a ton of time in proving procedures multiple ways before then, well, going ahead and mastering the procedure.

CCSS is untested (unless you count its imposition on 40+ states a test) so we'll have to wait and see if it moves the US up the meaningless PISA test rankings.