Because you can hear it, and it's said to not be a smart one. A smart monster would also do that but just be more stealthy with it and not be limited to the dark.
@PuppyBorkbutaccountgotwiped That goes the other way too. just as much as you can hear it is the same as just as much it can hear you. IT may not be able to SEE you, but it might HEAR you.
Yeah, but then you can just stand still and evade it. Assuming it can't see in the dark and you're smarter than it, the darkness will actually be disadvantageous.