It can be because the WW system is to some extent arbitrary. Zero-point veggies have zero points because whoever developed the points system decreed it should be so, not because those veggies have no calories. It's not a matter of being strict; if you're doing points, zero point veggies have no points by definition. If you stall, you might choose to limit your veggie intake somewhat, or not eat all your points, or add more activity (but not eat the activity points), but zero point veggies don't have points.
I didn't do WW to lose my weight. Out of sheer morbid curiosity, I once ran one of my typical day's foods through a points calculator, and came out with something like 36 points, even without capping fiber, and I'd have been allotted 20 base + 5 of flex plus 1 or 2 activity - so not nearly enough. I do better with more fat and fewer carbs, and the points formula really punishes fat.