unfortunately they never are. Brightness-adjusted, that is. Everyone installing lighting fixtures these days believes they must be daylight-level bright. The only ghosts you see are afterimages if you happen to look straight at the streetlamp ...

(I find it odd; dark-adapted eyes see a lot, including movement in shadows or low-contrast obstacles - after all, our bodies know how to see well at moonlight levels of illumination. Why are we so keen to kill this ability?)

Because

1) Humans night vision is significantly worse than your regular vision. Low light would cause more accidents, eg.

2) The elderly have pretty terrible night vision. Your idea would exclude them from half the day.