This is a thought in progress. A little rambling.
My wife is a combat rogue. Always has been. When she joined the game she fell in love with being a rogue, and she asked what the highest damage version of rogue was. I went off to the internets, and came back with the answer: Combat Sword build. So that's what she chose. When we got to the endgame, she did the most damage in our 40-person raids, virtually every raid. She gave the other dps people fits. (although she never spammed damagemeters) She flourished in that role.
When TBC was released, the raiding game was suspended and everyone is back to the beautiful leveling game for a while. In TBC leveling, there are quest daggers given throughout the leveling process, with rogues in mind. She thought, "why not experiment?" and then rebuilt as Combat Daggers.
Guess what? Combat Daggers is simply more fun to play than combat swords. Managing position and Backstab is more fun than mashing Sinister Strike x1000. To non-rogues, I'm sure this sounds like a minor distinction. It sounded that way to me, and I told her so.