Fighter pilots are expected to eject out of their aircraft in case the aircraft is not recoverable. An ejection always involves risk. You never know where and in what awkward condition you will land. Your question of survival comes later only once your head is safe.
The helmet also serves to provide facilities for a sound proof radio communication, attachment for oxygen supply, attachment for night vision glasses(NVG) and in many aircraft, helmet mounted display is also provided so that the pilot need not divert his attention frequently towards instrument panel.
few more details in following sliders,