Actually it doesn't (scratch very easily), comparatively speaking.
Very sparingly sprinkle some grit on a table, rub an iPad / Macbook Pro lid over it for a few seconds putting some force on it, then do the same thing with a Surface Pro 3 - and you'll see that the Surface actually shrugs off more damage than the Apple's. This is due to the superior surface treatment on the MS tablets which apparently they're finally getting peel-free with the 3 (though early days, eh ha).
The real problem is that the Surface is totally flat (i.e. 100% flat surface contact area), and also has no rubber feet as standoffs compared to a laptop, so regardless of the superior finish (which does stave off the scratches for longer than regular anodising under the same handling behaviour) you'd need to basically armour this thing in order for it to avoid constant road rash as it's handled and put down on surfaces daily. It's better than an iPad, but not indestructible. It kind of surprises me that reasonably smart people can't seem to abstract this.
If you want to avoid the surface contact referenced above, you need standoffs - decals or small unobtrusive stick-on pads on the corners.