I'm an agent, I do a lot of agent stuff like sneaking and sniping. Consider the following scenario, which has happened to me on several occations:
So, you need a piece a equipment or whatnot and take a mission some levels above your own. Since you're an agent, you can't engage any of the enemies (and survive) so you have to rely on your stealth.
After half an hour of careful sneaking, moving around high perception reds, sneaking behind the backs of others, you reach the goal of your mission: some item your employer wants returned. But, alas, it's guarded by some red mob which promptly attacks you.
Now, of course, you try to do the only logical thing: snatch the item before their very eyes and get the heck out of there while chanting "All your stuff is belong to me".
But you can't, and that sucks!
Please allow me to pick up items while engaged in combat.