Why private servers use 1.12 talents?

Hello there.
This is the first time i've played on a private server, i've been playing WoW since 2005, played non-stop up until the end of WotLK, on and off after that and now i decided to try to bring back a little of that feeling we all had in Vanilla WoW.
But i don't understand why all private servers start with the end of vanilla talents. Wouldn't make more sense for them to be updated when the the content is being released? Not to mention that the 1.12 talents are the most balanced in vanilla, which makes the fights in raids easier.
Are there any technical limitations? The original game can be easily found (i have mine, and many players have theirs), and there are still sites with the old patches.
This is the first time i've played on a private server, i've been playing WoW since 2005, played non-stop up until the end of WotLK, on and off after that and now i decided to try to bring back a little of that feeling we all had in Vanilla WoW.
But i don't understand why all private servers start with the end of vanilla talents. Wouldn't make more sense for them to be updated when the the content is being released? Not to mention that the 1.12 talents are the most balanced in vanilla, which makes the fights in raids easier.
Are there any technical limitations? The original game can be easily found (i have mine, and many players have theirs), and there are still sites with the old patches.