Board Thread:Lore Discussion/@comment-24.52.19.149-20141122005246/@comment-13446185-20141122024312

Because the Aldmer were the original Elves, in which all other Merish races are derived from. The idea of them promotes unity of Elven kind, which sort of fits into what the Aldmeri Dominion is about, the reclaiming of Elven dominance over Tamriel. It coincides with how the Alessian, Reman, and Septim empires are often called the "Empires of Man".

It should also be noted that the Altmer believe that they are the closest decendents of the glorious Aldmeri master race, and claiming that they are the true descendents of the Aedra (despite the fact that all mortals are descended from the Aedra).

Vanus Galerion is certainly not an Aldmer, that race split apart at the end of the Dawn Era.

As for the Khajiit, read this book.