Because George Lucas is a hack. Also, the emperor was leading him on with the promise of teaching him how to raise the dead(his mother) with the force, so it makes sense if you think of it that way (but it also makes Anakin a gullible subordinate). Did I mention that George Lucas is a hack?

The only thing I can think of is fear for the emperor. Or he had more to teach Vader about the ways of the dark side.

My Dad had always told me that the emperor was keeping him alive, so vader died when the emperor died

Ummm....he did kill the Emperor.  Ever see the end of Jedi?

"

My Dad had always told me that the emperor was keeping him alive, so vader died when the emperor died

"

Because Vader need some one to study the force and know how to beat dead.

Well after making an ass out of himself and allowing Windu to die, killing all those young padawans, fighting Obi-wan to near death, and THEN Padme still dieing he might as well just stay at the emperors side.
Plus Vader didn't want none of the Emperor. The Emperor would stomp Vader easily. It cost him his life when he killed him in ROTJ.

" Did Obi-Wan cut off Anakin's cajones too"

Because the Emperor is about eight times stronger than Vader was at his prime? Vader's connection to the Force was greatly weakened after he lost his physical body, not to mention that he had no reason to try and prevent people from dying since he knew Padme would never forgive him for "killing her". The Emperor was the only thing he had left, his only friend in the world, why would he kill him? It was only when he discovered that he had a son that he saw the Emperor as the disease he really was.

" @FadeToBlackBolt:  But why or how does Anakin Skywalker's accident, losing his limbs, weaken his force, or his ability to use the force, or his ability to learn more of the force, because isn't the force a matter of the mind, or of believe, and not dependent on matter, on size, on physical things, on Anakin's physical body, right? "

" @JoeyArnold said:

" @FadeToBlackBolt:  But why or how does Anakin Skywalker's accident, losing his limbs, weaken his force, or his ability to use the force, or his ability to learn more of the force, because isn't the force a matter of the mind, or of believe, and not dependent on matter, on size, on physical things, on Anakin's physical body, right? "

Because George Lucas is a hack. "

" @FadeToBlackBolt said:

" @JoeyArnold said:

" @FadeToBlackBolt:  But why or how does Anakin Skywalker's accident, losing his limbs, weaken his force, or his ability to use the force, or his ability to learn more of the force, because isn't the force a matter of the mind, or of believe, and not dependent on matter, on size, on physical things, on Anakin's physical body, right? "

Because George Lucas is a hack. "

Fixed it for you. :P "

@jeronimo: how can you put Dooku higher than windu and sidious? no way Dooku is higher than those 2, I think

This work for me.

The sith rule of two.

"Two there should be; no more, no less. One to embody power, the other to crave it."

―Darth Bane

He has, many times. It's just that because the Emperor is too powerful (Trust me, he is), Vader never chooses to go head on with the Emperor without an apprentice. He needs to have an apprentice that is powerful with the Force. As seen in Star Wars: The Clone Wars, the Emperor easily defeated Darth Maul and his apprentice, Savage Oppress. And those two were very powerful Sith Lords. Darth Vader knows that the Emperor is more powerful than him so that's why he never tries. That does not mean he never thinks about overthrowing the Emperor to take control of the Empire. If he could, he would've done it a long time ago. That's why Darth Vader always looks for an apprentice such as Starkiller and the failed attempt, Luke.

Because Vader is factually only 80% as powerful as the Emperor. He simply is outmatched and he knows it, which is why he raised Starkiller and why he tried to recruit Luke to aid him against the Emperor.

What'd be the end game to that? Before learning that Luke and Leia were alive, Annie really didn't have any incentive for killing Papa Palpatine. He didn't want to rule over the empire or anything like that, he just wanted to be a Jedi Master and be with the love of his life, and since none of that ain't happening, all he his is being Sidious enforcer. He's life is already devoid of meaning, killing papa would just devoid it of purpose.

Plus, Papatine ain't no punk b*tch.

Vader isn't actually 80% of Palpetine.

If Vader tried to kill Sidious, he would have been one-shotted.

And Mace is not better than Sidious in sabers.

@necromancer76:

Considering that Yoda couldn't one shot Dooku and Palps couldn't one shot Mace, I have trouble believeing Sidious would one shot Vader.

He'd dominate Vader for sure, but Vader isn't getting blitzed.

@emperor339: Sidious could one-shot with lightning. Vader is weak to lighting and Sidious can already disintegrate people with lightning anyway.

Because Sidious would disintegrate Vader.

There's a private board for Darth Vader... nice.