When I first saw the thread, I thought A_F_L_M was putting us on.
But maybe not. When I was younger, I never bothered with a separate pillow while camping; the idea was laughable. But as I get older and considerably less flexible, I take a pillow when I can. Not backpacking (yet) but definitely for a base camp or car camp.
Sleep is health and energy. Sleep gives resilience to deal with adversity.
Besides which, without a pillow, I snore like a grizzly. Loud enough to make people killin' mad. That makes it a survival tool.