Because I love Sokka, and I love his war-paint too. I think we only get to see it once, which is a pity because it's really kind of awesome.
Sokka took a deep breath and dipped his fingers in the dark paint, swiping it under each eye. The orca-seal war-paint was supposed to give warriors courage, as their brothers around them prepared for battle.
Sokka put his on alone.
He understood why the other men couldn't be here. He also understood that if he fought, he probably would not survive the day.
He couldn't just give up, though.
Sokka finished his paint and picked up his club, sliding his boomerang into its sheath.
He may not be a real warrior, but he was the closest thing his village had.