Why are there scratches on new bricks?
I have seen this happen with parts originating from older Lego part molds (dies) (like the 16L studded Technic beams in the 42009 Mk2 crane truck). My take is that the molds have been scratched during a maintenance operation but that the mold damage is still within tolerance for Lego.

Creating a new mold (die) is very expensive.