Maybe because that doesn’t fit the theme of a lot of classes and it could cause a lot more broken scenarios? “It’s a new mechanic for this expansion” isn’t much of an excuse when we’ve had things previously like jade, schemes, etc that not everyone got access to.

Also, Priest already has a minion that is giving reborn to things, and reborn is basically just a possibly improved resurrection mechanic. It’s only natural that priest would have far more mastery and support for this new mechanic (though its really making me question what the point of paladin’s quest was now…)