Get of your own stinking horse, I'm level 24 and I haven't even gotten halfway through Taris. And don't even try to make it sound like the people asking for this o-p-t-i-o-n are elitists trying to impress everyone. You're the one branding anyone who'd like the option as MMO greenhorns, it's pretty clear who the attention you-know-what is in this case.
I'm sure the XP gain is very smooth if you take PvP, space combat, heroics and flashpoints out of the equation, but if you don't, then at least I tend to outlevel the main content severely. And if you think I'm doing any of that to impress people, then go put your head in a bucket of water and inhale deeply. I do whatever I think is fun, whenever I want to do it and I would love to have the o-p-t-i-o-n to do it without ruining the experience of the main storyline.