Perfect example of dialogue tree needing improvement...

In addition to my previous response, another thing to consider is that the paraphrasing allows the specific dialogue delivered to change depending on some of the decisions the player has made prior to that point in the game without Bioware having to also program a change to the textual dialogue wheel.  These subtle "behind the scenes" changes happen in the Trilogy, often depending on how renegade or paragon Shepard is at that point.  If you want a few different YouTube playthroughs, you'll soon start spotting places where the dialogue wheels appear the same and the players do select the same option, but Shepard actually delivers different lines of dialogue.  

Sure, it's a convenience for them that, no doubt, saves on production costs and probably limits a number of potential bugs. If the visual dialogue wheel had to change to display every line possible at every point in the game regardless of the player's choices to that point, the odds of the wrong wheel displaying at the wrong point to in the wrong situation would go up astronomically.