Because they never died, and "man is destined to die once, and after that to face judgment." Hebrews 9:27
Elijah and Moses are proposed because of their presence on the Mount of Transfiguration.
But why not you and me?!
1 Corinthians 6:
6 Dare any of you, having a matter against another, go to law before the unjust, and not before the saints? 2 Do ye not know that the saints shall judge the world? and if the world shall be judged by you, are ye unworthy to judge the smallest matters? 3 Know ye not that we shall judge angels? how much more things that pertain to this life? 4 If then ye have judgments of things pertaining to this life, set them to judge who are least esteemed in the church. 5 I speak to your shame. Is it so, that there is not a wise man among you? no, not one that shall be able to judge between his brethren? 6 But brother goeth to law with brother, and that before the unbelievers.
Hmmmm ...