Number 03

@Dinardo

Yeah, because its a King. The King would interfere with the Queens authority.

I can pretty easily see how a king would fit into a hive, and how it'd work out well. It may seem unneeded- and that's because, well, technically it is! But just because a hive can well survive without one, doesn't mean he couldn't bolster it well. Queens, by official math shown in the second movie's trivia, lay 15 eggs per hour. That adds up real fast given they're laying constantly, and each and every egg not just needs a host, but the resulting Xenomorph is going to need food, water, and space to live like all the others. While more numbers means more Warriors & Drones to hunt for prey & hosts, it also means they're stretching themselves thinner to cover enough area to find all that food. A bigger hive is both more powerful, and yet, more potentially vulnerable. 

So what good is a King? A king can not only pair with a Queen to increase potential for royal offspring (she seems to mostly suppress her own genes for that to make normal workers, so adding his own would help up chances) which helps the species populations and hive numbers on that planet. This also gives potential for a Queen to become an Empress, if she can stay dominant over her neighboring daughters. He's a walking tank standing between the hive and any big threats. And, though warriors are plenty good at hunting, it doesn't hurt to have some extra muscle to take down bigger, better quality prey for the ravenous swarms. 

The hive doesn't NEED a King to survive. But he could definitely be helpful. He could definitely make a situation a lot scarier for anyone facing down that hive. If he helps a Queen become an Empress, well, that's even more fun potential.

I also kinda imagine him being akin to a bigger, better Praetorian in terms of ranking- he's not there to contest authority. There's no point- he can't lay eggs, he doesn't have telepathy or the right pheromones, he can't run the hive. But he is there to defend the Queen and keep others in line for her. Help keep it running smoothly. Like a second in command, the muscle for the brainpower of the operation. The hive is still a monarchy.

Perhaps less why, more, why not? It could work, and it could be great.