Why are unidentified runes wanted?

As the topic. I've seen people asking for unidentified runes and items. Why?

To unlock them! Once unlocked, you can use them with a pvp only character.

So you have to identify a Rune in an item to unlock it for PvP characters? That's what the 'You have unlocked so-and-so means'? Do you have to salvage the Rune to unlock it as well? Otherwise how do you know an item has a Rune someone wants without identifying it?

So do you only unlock runes if you identify them yourself? Or do you also unlock them if you acquire a rune that's already been identified?

Yes, you need to identify them yourself. Once you see "You have unlocked so-and-so" you can use it for a PvP character, you don't need to salvage it. Although if you want to use it or sell it you'll need to do so.

Also, once something is unlocked (skills, upgrades, runes) it stays unlocked so you can delete characters and not have to worry about having to unlock these items agian.

As far as buying unidentified runes there is no way of knowing it will be what you wanted, but you will at least know that class it's for by the graphic on the rune. It's a gamble on both people's end.

So how come I've unlocked the same runes several times with different characters? With my first character (en elementalist) I found a minor vigour rune and it told me it was unlocked, and I also saw it available when I created a PvP only character. Then when I created a PvE warrior, I unlocked the same rune again after a little while of playing. If I've already unlocked the rune for PvP characters, why is it tellling me again that I've unlocked it?

Each character is new and everything will say it has been unlocked. As far as I know it only needs to be unlocked one time by a character for it to be available in pvp. Someone correct me if I am wrong.