And Really we have had several planetary sized disasters from the Doomsday Machine destroying full planets, to Nomad, to the damned space aomeba (sp). And just because the planet is destroyed doesn't mean that the Vulcan's people are all destroyed or their importance to the Federation.
I wonder what would happen to America if 90% of its population and territory were destroyed? You think this wouldn't have apocalyptic ramafications for the American people and the world at large? And comparing the destruction of Vulcan to unnamed meaningless worlds makes little sense.