Yeah I don't really get the logic of Alien design requiring too much logic. They do need a basis in reality, but barring dreadlocks when we don't even know the biological function despite including dorsal tubes or the Alien even having a skull (a skull that includes eye sockets no less) is kind of odd.
Really the biggest sin of the dreads is that the Alien skull isn't suited to them. The Predator's frill-like skull allows them to drape better but on most if not all PredAliens it seems its there if only because its on the Predator. Really all one needed to do was just include the frill, and the dreads would drop just fine. You could still even retain the penis shaped skull like that but the dreads just drop down or if only to the sides of the frill.
Just putting some mandibles on a warrior or drone just isn't as impressive to me and lacks the shock. The Predators see infrared and we know the Alien doesn't show up well to them. The design at the end of the day is for us the viewer, because we can see it clearly, the Predator can't. So from the perspective of an audience member, they should look a bit more theatrical and with the dreads you can make head movements dynamic and bigger.