Damage loss over distance makes the most sense(and there's a reason why nearly every game that has shotguns in them implement this), and no one likes inconsistency. Spread in itself adds a layer of luck to it that can make shotguns already an inconsistent weapon, adding random damage on top of that is just a slap in the face. If shotguns do high damage in close-quarters, that's how they should be used. And as far as I know, nothing stops them from doing that right now since they do damage WITHOUT dropoff.