Because there are no night maps planned for release yet... refinery had great lighting in the alpha phase, but they darkened it making a flashlight useful. Instead of flashlights, just brighten the map about 10-20%, problem solved.
I just don't understand what the hell is wrong with you guys still not understanding flashlights after years of playing INS. The point was never to see in dark areas. It was in the game before the night maps. The first goal was always blinding people. And it works amazingly well.
We need them. They were in the first alpha I believe, but utter bugged.