Good point. I thought the whole purpose of penetrating north into Pennsylvania was to draw the Union forces west and away from the Confederate capital of Richmond and the rest of Virginia. That’s it.
That was half of it. He wanted to get away from Jefferson Davis, who talked about sending much of Lee's Army west to relieve Vicksburg. But the biggest part was to get out of Virginia and live off of the Union for a while. His Pennsylvania campaign was a huge hunt for supplies. His goal was to gather enough supplies for his army to see him through the winter. His commanders reported to Lee on a regular basis just how much they had accumulated.