When playing your 3rd or 4th class, having to repeat SAME planetary quest arcs and miscellaneous quests can be very, very distracting. Especially for some people. It's easy to get lost and forget "why", "to who" and "for what" we're heading in the direction the quest marker inicates. It is also easy to forget and lose track of our own quest and companion chat.
I have all my character slots full now and I would love to replay my Sith Warrior story line after the entire year. It was a good craic and I'd love to "amend" some choices before Makeb. I'd love to wear the armor I want and gathered over the past months and properly "prepare" how my story, my gear and companions will progress in different chapters. And without having to do mandatory planetary quests.
Daily quests reset. What's the problem in putting a "reset button" for our story lines (and maybe planetary quest arcs in the future)? After that we just travel to starting area and walk into our very first instance. We're missing the intro subs but, hey, you care? Few days/weeks cooldown on it. And it will hardly affect continuity and like. I finished my story line months ago and recently I decided to finish all my planetary arc. I was still referred to as Baras' apprentice and someone who is still an apprentice though I am a Darth for good few months.
So no worries, no one will care.