>>212157379In the first movie, the alien was abducting people and turning them into eggs. He only kills Lambert and Parker because the alien is attacked. If the ship hadn't blown up, that single alien would have created 2-3 new eggs that could survive hundreds or thousands of years before restarting the cycle. Let him loose on a bigger ship, or a planet, and at that rate a single alien could create a colony in days. In the second movie, we see just that, and the entire colony is turned into aliens soon after.
If it weren't for Ripley blowing them up every time she meets them, the aliens would be an incredibly effective lifeform.
The queen/hive is stupid though. They shouldnt be space cockroaches. If Cameron wanted a big villain for the ending, he should have done what Alien 3 did with the cow.