Yup, this is true that the pressure is too small, but the true explanation is not justified yet. Nevertheless the common sense is that there is a lubricating film of water or at least anomalous ice. For an overview, see: http://lptms.u-psud.fr/membres/trizac/Ens/L3FIP/Ice.pdf. read more
The assertion that the skate does not exert enough pressure to melt ice is wrong. Imagine that the skate is lowered vertically until it touches a perfectly flat surface of ice. The initial contact area (before the blade starts to sink into the ice) would be incalculably small and the initial pressure incalculably large because of curvatures. read more