Best explanations that I can come up with for not launching the escape pods:
1. The Saucer hit the atmosphere very quickly after the core explosion. Launching the escape pods would have meant dropping the shields, causing the saucer to incinerate. There's no way in that short a time, they could have coordinated all pods to launch simultaneously to ensure all survivors got off the ship. In addition, the pods were located on the outer hull, they would be instantly damaged when the shields dropped to allow them to launch.
2. The escape pods may not be powerful enough to achieve both launch and a soft landing while within an atmosphere.
Works for me.