Because, very simply, the US was waiting eagerly for the town to fall. There were all sorts of reasons for this, and none make any real sense. The two biggest are: (a) The hick Islamists running Turkey tilt toward IS and hate Kurds, all Kurds, with the same insane virulence that Turks hate all their neighbors, and especially any minority that dares to identify itself as non-Turkish; (b) The YPG militia defending Kobane is linked to the PKK movement, which is nominally “Socialist,” and American apparatchiks, no matter who’s officially in charge, have never un-learned the anti-Commie nonsense they learned at Georgetown; and (c) The “brave, doomed defenders of Kobane” were worth much more dead than alive, much more in defeat than in victory. If they lost, they’d be beheaded by the vicious loons in IS, and those severed-head videos would be great US agitprop, a great little way to put more pressure on Turkey over the theatre the US really cares about—Iraq.