Any reason to complete personal story?
Only if you want 100% map completion. A few spots require story-mode. Other than that it’s not required for anything I think…
Just who the hell do you think I am!?
Hmm, interesting
For now there are little things affected by story (such as New NPC in your instance depending on which path in your PS you chosen) but as the game progress, if Anet follows how they handled GW1, you may have to progress in your personal story to access certain future areas.