Always thought Hicks and Newt had served their purpose, story-wise. Plus, as others have said, the idea of the three of them becoming some kind of family unit pitted against the Aliens always struck me as pretty cringey, so I'm really glad they at least negated that.
Maybe I'm a nihilist, but to be honest, I always appreciated the balls the third film had in killing off all of its main characters, even if the execution was flawed. It certainly makes it stand out among big franchise movies, where anyone important is almost invariably protected by plot armour.