The very inadequacy of the Old Covenant mediation was designed to make men see the need for a mediatorial ministry of greater efficacy.  To have a broken-down old car to drive is much better than nothing, and one may be thankful for it, yet the frustrations of driving it make you long for a good one; and similarly, the experiences of living under the Old Covenant could not but arouse longings for something better – a better covenant, founded on better promises, holding out a better hope, and resting on the efficacy of better sacrifices. (J.I. Packer, 18 Words)