Why the pursuit of unlocking so much?

Think about it, There is almost no incentive if you've played through the game. Your PvE char has more than likely.

A.) acquired better weapons
B.) Better armor look
C.) Better weapon skin look
D.) Is more than likely using the weapon w/ stats you wanted.
C.) Runed up w/ the runes you want

I mean fine, the thought of creating a perfect char from the get go is nice, however, character creation is very very limited, Weapon skins are set to the most boring, non ascended armors only w/ up to 3 selections and no custom coloring your armor/weapons so everybody gets to look alike.

Also, I haven't been to HoH yet, but would it show on a pvp only char? It doesn't show on mine(which I created just to be storage mule, I guess thats the best use for em).

The purpose is so that your next character can be a pvp only character and you don't have to spend 2 weeks finishing PVE and finding new equipment for it.

Hall of heroes is the last map in the tombs of primeval kings tournament

That is of course assuming that you want to do pvp in the first place..