Because of decoherence and the linearity of the Schrödinger equation, you can get a very good approximation to the behavior of the wavefunction over a certain set of configurations by 'starting it off' as a very localized mass around some configuration (if you're a physicist, you just say "what the hell, let's use a Dirac delta and make our calculations easier"). This nifty approximation trick, no more and no less, is the operation of 'state reduction'. If using such a trick implies that all physicists are closet single-world believers, then it seems astronomers must secretly believe that planets are point masses.