I know, but given that people trying to lose weight generally have a problem overeating carbs, "giving yourself credit" for fiber carbs overcomplicates tracking and most people tend to underestimate digestable carbs taken in, so counting fiber against your quota can help correct for that error. Trying to "game" your carb intake by padding with fiber will work for the ultra-disciplined, but will probably just result in a false sense of intake levels for most people.