So why does this sound so personal for you? Like someone's trying to steal your dog and claim it was theirs originally? No one has asked for anything their faction does not already have...at least at the baseline. There are Blood Elves in the Horde and High Elves in the Alliance. Its been that way since the Blood Elves joined the Horde. No one is stealing from you in any way.
If you think High Elves will steal from the Horde, than the Horde has a problem with retention, because Blood Elves wouldn't go away. This isn't a request for making the Blood Elves into High Elves, its a request to make the High Elves that are already in the Alliance playable.
As to why do you see 300+ pages for High Elves and not the others? The other races aren't contested by people. There aren't multiple appearances of Ogres in the Alliance settlement, nor screen time given to them even in the Horde much. Their aren't San'layn in any Alliance questing hubs, and only recently in Horde questing in BfA. Wildhammer's aren't seem in Horde questing hubs, nor do they get much screen time in the Alliance story.
But High Elves? We have them in multiple questing hubs in the Alliance. In Stormwind. We see them in Dalaran and they are given a relatively large amount of screen time relative to several playable races. And than, on top of that, there is the Blood Elves that get their own screen time for the Horde and several questing hub, plus of course Silvermoon, though you don't see all that many Blood Elves in the other Horde cities (NPCs). So both sides have these similar elves in their questing content, quest hubs, and a share of screen time in their faction questing content. Yet one version is playable and the other is not. The one that is not has been requested to be playable since before the other joined the Horde. So therefore 300+ pages of thread due to a fairly unique situation within the World of Warcraft. A species that is divided between two faction for a decade (our years, not game years), one playable, one not. Of course people are going to want to play the group that isn't playable, yet is present and given screen time.