Talking about District-9
In an alternative 1982, an alien ship has inexplicably stopped over Johannesburg. When investigation teams enter the ship, they discover a population of sick and malnourished extraterrestrials, identified derogatorily as "prawns".
So the reason behind that aliens let them be treated like hostages could be explained with this. They were weak and sick. So they avoided war at beginning. They turned the place into slums and was living there miserably.
But the movie plot starts after 20 years have been passed. So why didn't the Alien attack with their advanced weaponry and free themselves from such cruelty of humans. They were having advanced war suits that Wikus used later. I'm guessing that war suit needed to be initialized by the remote ship that later took Christopher Johnson(Alien) to the mother ship. But they had more advanced guns, bombs. Why became slaves for over 20 years when they could try to fight back.
Am I missing something here? Is there any reason for which they were not attacking?