Interest income from deposits with banks u/s 80 c

In the case of Deposits in NSC the interest earned from NSC also qualifies for deduction u/s 80 C. But interest income accrued from similar deposits u/s 80 C made with banks is not deductible. Why ? As in NSC'S the banks also follow a lock in period of 5 years and so one cannot withdraw the interest earned each year. This priciple applies in the case of interest earned from NSC's - so why this same priciple should not be followed for bank deposits u/s 80 C also.