Only the Dragon is a relevant reincarnation, and possibly the Heroes of the Horn, because they have specific purposes. For everyone else, it's a chance to get stuff right or do new things. What's the point if you're shackled to the same person forever? One life, he had Ilyena. This one, he has Elayne, Aviendha and Min. Next time it will be someone else. "'Til death do us part" is not just fancy talk for forever.

Then there is the implication that the three of them are not real people or not their own people, that they are only part of a person and in the case of all four women, all that matters about them and their existence is their relationship with the Dragon. That Ilyena is being reborn specifically to be a companion to the Dragon and that her soul is being split apart, whatever that means, so it can do more for him, reduces her and her triple reincarnation to accessories.