Time to come out of my dormant slumber of not posting for years to talk about this. ArenaNet has addressed this countless times. The reason race changes don't exist is cause the personal story is tied to your character creation choices.
However, there is a way to introduce a race change to the game and make it work. I've played this game since the beta and the one thing I've noticed through multiple characters is the majority of any race and personality tie-ins stop at level 30 or about when you meet Tybalt in the original story and start uncovering the story about Zhaitan. The first 30 levels of the story or so are all your character introduction and racial tie-ins. You can introduce a race change but make it only available to use after you have reached a certain point in the story as well as reaching a certain level requirement on a character. This would then save the dev team untold hours of work and all that would left to do is go through any of the story afterwards and "clean up" or rework any miscellaneous racial stuff that doesn't relate to the main story of Zhaitan. As far as I can recall, any of the expansions have no inclusion of your racial or personality background.
Now, whether that work is worthwhile or can turn a profit for ArenaNet is not something I can't predict. Whether ArenaNet does introduce a race change or not doesn't matter to me and I don't blame them for not putting in the work to try and introduce something like that. What I mentioned earlier is merely a suggestion as I have no way of knowing how the game's backend works. That being said, if ArenaNet ever does introduce a race change, awesome! And hopefully, the above suggestion helps in figuring out a way to introduce one.
