Fighter's are taught to defend themselves, rogue's are tought to exploit weaknesses.
A fighter that goes out of it's way to dish out a lot of damage can. And the rogue that acts as a fighter's sidekick can give the fighter a chance to get those interupt attacks and therefore do more damage. A rogue needs the fighter to flank and mark, so that the rogue gets his SA, and hopefully stays alive. The rogue, on the other hand, provokes some OAs [which being so charismatic is hard to hit him with] and let's the fighter do more damage.
A rogue without sneak attack is doing less damage than a fighter, especially a great weapon fighter. And a rogue without a defender is going to get himself killed. Part of a fight is not dying, not just the part where you kill the other guy.