PU sales 2nd quarter (from an interesting source)

I still don't understand why GM makes the Chevy and GMC pickup trucks under 2 different names still at this day.I figured years ago when they restructured and dumped ponitac they would have done the same with either the Chevy trucks or the GMC's.

Them having both would be like Ford coming out with a FMC pickup line and only changing the badging everywhere on the truck...I just don't get it...