Why do you need two entry level brands?
Chevy is as entry level as Saturn is today. The argument for Saturn being entry level was solid in 1990. Today, not so much as their lineup has expanded to include SUV's, minivans, sports cars, etc.
No need to have Saturn when you have Chevy.
The case for Pontiac vs Buick is a little less clear-cut. Arguments can be made for keeping both of them. I suspect they kept the more profitable (or less losing) of the two.
Many Pontiac dealerships also had GMC. If I recall, GMC is being kept, so are they really getting rid of that many dealerships by getting rid of Pontiac?
Seems like getting rid of Pontiac is more about collapsing a division than it is about closing dealerships. They may not even get rid of the Pontiac name, just not have Pontiac as a separate division, from what I've read.
So GM is selling what isn't "core old school" GM, I.E. Hummer, Saturn and Saab, and simply doing away with the separate division status of Pontiac.
I wonder if Pontiac won't be a "tuner" shop for GM at some point in the future.