Because having "night" be "daytime but with stars in the sky" is stupid, and the art team should've been embarassed by it. I fully understand that realistic nighttime is out of the question in an MMO (at least one where day/night goes by real time), barring some sort of gameplay element to let you see. But it should at least look darker at night than during the day. Vanilla WOW was fine with its day/night cycle. I actually quit playing until the darker nights were announced, because the way it is now absolutely *destroys* immersion.
The only way realistic nights could happen in an MMO is if the day/night cycle wasn't the same every day (like ESO, where you get 2.5 hours of day, then 2.5 hours of night), AND there were gameplay elements to let you see at night. I don't think anyone is asking for realistic night. But night should at least look *somewhat* like nighttime.