The first and most important reason is that the Sniper will be able now, thanks to the Huntsman, to pin enemies against walls, score a critical shot for all headshots, while full power shots only need one second to charge. So, yes, we can agree that the Sniper will now become better at close-range combat.
And if you are one of those people who consider that maybe Valve are exaggerating a bit with the introduction of bows and arrows in Team Fortress 2, the devs have the answer: these weapons are the only cause for the extinction of dinosaurs. Yup… can’t argue with that impressive logic, can we?