Day / Night cycle is basically you resting. The camp is shown during night, rest of the world we've seen so far during the day.
As designed, but it would still be cool to adventure at night, there are reasons to adventure at night. For those that love playing as rogues, the night is essential as all the interaction for vision be it natural like darkvision or torches etc. We do have that when inside, but night adventuring also introduces monster encounters not typical for daytime.
