As it has been said before and will be repeated, it’s cause the writers had to give her a name from a legacy to link her to an important legacy that had nothing to do with her. Even her backstory of being some stowaway who is secretly a Lothar is like something out of fanfiction. I’ve seen way too many stories where the special person is special all along. And then in the game, she outshines Anduin at every turn with her holy powers while he forced to sit back and be meek and pathetic.
We know what her purpose as a character is. We know why she wields the name. It’s just a matter if you are bold enough to admit it.