The c-axis tunneling matrix of high-Tc superconductors is shown to depend
strongly on the in-plane momentum of electrons and vanish along the four nodal
lines of the d(x^2-y^2)-wave energy gap. This anisotropic tunneling matrix
suppresses completely the contribution of the most extended quasiparticles in
the vortex core to the c-axis tunneling current and leads to a spectrum similar
to that of a nodeless superconductor. Our results give a natural explanation of
the absence of the zero bias peak as well as other features observed in the
vortex tunneling spectra of high-Tc cuprates.Comment: 4 pages 3 figures, minor corrections, to appear in Phys Rev