It's partly that. But a lot of the casualties in Afghanistan are happening in small bases up on the mountainous frontier with Pakistan. A Taliban force sneaks up close (a la the Viet Cong) and lobs a bunch of rockets at these observation posts while trying to overrun them before the (US/NATO) aerial firepower kicks-in. Sounds familiar, doesn't it?
Why are we maintaining small bases on the border with Pakistan when we could eliminate the Taliban one by one with the use of Drones?