The removal of these 32,000+ lines of code from Mesa for this Intel Gallium3D driver come sine the i965g driver barely worked and there's no active stakeholders interested in the driver. The i965g driver also doesn't support the latest Intel hardware like Sandy Bridge and Ivy Bridge.
The i965g driver was largely worked on previously by (Tungsten Graphics) VMware and community members. Intel has never officially supported the Gallium3D bandwagon. Having this driver in mainline Mesa just adds a maintenance burden when Gallium3D developers are working on architectural changes, etc.
Meanwhile, the "i915g" driver is still around for pre-965 Intel integrated graphics processors. This driver is at least actively worked on (thanks in large part due to Google and their interest of this unofficial driver for Chrome OS) and works fairly well on the supported ASICs, including the i945 IGP common to early generations of netbooks. The Intel 915 Gallium3D driver also performs well, but the i965g driver just never made it as far.
It's possible down the road that someone may pick-up work on this driver again and return it to mainline Mesa, but there's no active interest at the moment and Intel isn't yet backing any Gallium3D driver.
The i965g driver was dropped via this Git commit. The official "i965" classic Mesa DRI driver is not affected in any way by this action.