All that is true, but that's just the movies. They managed to display the creature like they wanted with less gore but we still got the idea of it like a creature that kills everything in it's way and it doesn't do it in a nice way. There is always blood, brains and asses flying around.
In a game you have to SEE it. You are the alien, you kill stuff, it bleeds. You don't just thump someone on the head and he drops dead. Or even if you are just playing the colonial marine, you have to see the burster coming out, alien impales your team mates with his tail, it's what the game is about. People expect it to be bloody and it's safe to say that some like it.