Because humans have dark colored cells behind their retinas that absorb light rather than reflect, so a realistic non-nocturnal humanoid's eyes wouldnt reflect light in shadow. We could argue that Hroth and Miq' eyes could structurally resemble a cat's eyes more and have a tapetum lucidum that would reflect light but that may be very difficult to produce a natural appearance at the scale of the game. So if the idea that because the races are humanoid, their eye structure would resemble a human's eyes, they would shine in the dark.