For those who say magazines are relatively cheap and a person is going to buy what they want anyway, why worry about only one mag, I'd say why bother with any mags at all? Just let the LGS provide one for in-store testing of the lock back (unloaded of course).
For a new shooter or someone not as "into" 1911s, getting two mags would be a distinct advantage.
With Kimber providing only one mag, it seems like it's urging buyers to test the waters elsewhere, not only for mags but maybe guns too.
Actually, I always thought manufacturers ought to provide 3 mags, but that's another wishful thought.