Its because the 0.25 lux used as the cut off of a beam's range is actually about useless at long distances....maybe you could tell SOMETHING was out there, but not a man with his arms full of firewood from a man with a firearm, etc.
If getting to your hotel room bathroom at 3 am with night adapted eyes, 0.25 lux is not too bad...and for other fairly close range large motor tasks.
..But, if the same 0.25 lux is on a target 200 yards away,...well...think about how hard you need to focus your eyes in DAYLIGHT to resolve details on something 200 yards away.
You'd use your fovea, the sharpest part of your vision...roughly a 2% cone of vision....to see anything at that range...
..except THAT part has the worst night vision...so you need more light to see details with it.
To avoid bumping into furniture, peripheral vision is fine...but try threading a needle, or seeing someone laying in the grass 200 yards away with it...much harder.
If you do the same range calculation with a higher lux cut-off, you see a dramatic drop in range.