I always thought it was because Stuart didn't get back in time but rode around showing off and taunting the Yanks. His information could have changed the outcome.
I look at Stuart's irresponsible actions at Gettysburg as part of what overtook the south and led to their defeat at Gettysburg; that is, the idea of their own "invicibility".
They all got so full of themselves, and got so used to being up against incompetant Union commanders, that when they finally ran into people like Meade, Grant, Sherman, etc, they got sh!thammered.
Stuart's actions at Gettysburg are a perfect example of the south's belief in their invicibility. Lee's ordering Pickett's Charge is another example. He had come to believe that his men could do anything he asked them to.
Unfortunately for him, Winfield Scott Hancock was on the other side of that wall.
Lee didn't have his "eyes" b/c Stuart was raiding. He made the call to go to battle without the lay of the land, hindsight says bad move (so does Sun Tzu). The leadership void from the events at Chancelorsville were more apparent than ever, though Longstreet had the right idea on the flank.
Re: 46 - what is becoming clearer?
I always thought it was because Stuart didn't get back in time but rode around showing off and taunting the Yanks. His information could have changed the outcome. That's one of the more persistant myths of the Gettysburg campaign, along with the one that Rhodes went to Gettysburg to rob a shoe factory. In fact, Lee retained half his cavalry with him while Stuart went off with the other half.