Because there's no reason for Aliens to take mental ability from hosts. As Xhan pointed out, they look for patterns in the environment and in prey with entirely different priorities compared to other organisms. Taking mental attributes from hosts can't benefit the Aliens, but there
is the possibility that it would interrupt their thought processes enough to make them less effective survivors and hunters.
The reason Aliens take physical traits from their hosts (which seems mostly limited to skeletal structure) is that having the same locomotive functions as large organisms from the environment allows them to dominate the terrain. Aliens don't need to know exactly what grass or water is, they just have to understand how potential prey organisms interact with those environmental elements. Having the mentality of a rhino in Africa wouldn't assist with that, but having a mentality with alien priority would.
As for the novelisation -- the EU is too incongruous to draw from reliably. Obviously, everything to do with the post-
Aliens narrative is down the drain with the implicit retcon that came with
Alien 3, and then you have things like some guy beating up multiple Aliens or Alien/Predator/Human hybrids that throw facehuggers. I think there's even one novel that tries to claim that humans created the Aliens, but I'm shady on the details of that (heard it second-hand). In addition, Rebellion specifically pointed out that they were drawing on the first two
Alien films and the first
Predator film primarily.
QuoteYeah, and what we observe is that the Aliens the Rookie and the Predator encounter adhere to predictable patterns and end up dying, even when they attack en masse and from multiple directions. All it goes to show is either the Rookie and the Predator are REALLY amazing and substantially better than their peers, or (as mentioned earlier) Six is also better than her peers.
I suspect that's mainly due to AI limitations. In any case, the Aliens had more complicated combat patterns than both the human and Predator adversaries, so by comparison we can make a good guess at what the game was trying to express.
My interpretation, overall, is that Rookie, Lord and Six were all essentially normal members of their species that were in the right place at the right time to develop the know-how they needed. Lord was an experienced enough hunter to qualify for Elite status, after all, and Rookie had complete marine training and the luck to take on a couple of Aliens one-on-one before moving on to multiple target scenarios. I don't see anything inherent about them.
As a disclaimer, I have a nurture-over-nature perspective on life in general. If you disagree with that perspective,
we're destined to do this forever.