Downplayed: Jack is not that hurt, but is very clearly outmatched by Tom in every way, but continues to fight, even though he could simply admit defeat.
They have nowhere to flee, and even the slightest chance of injuring their foes is better than nothing.
They're just trying to buy time while their allies escape.
Jack doesn't have any self-preservation instinct; at all.
They are members of an army defending their home city; loss of the city will lead to looting, plundering, and quite possibly loss of their family members. At the worst case scenario, their refusal to surrender means that there are less invaders to pillage and more of a chance for their family to avoid a looter.
"Always be ready for them, lad, until you see they're all dead. They never retreat."
"At least you don't have to worry about how any survivors might have gotten away and regrouped. They all attacked to the death."
Conversed: "I might not be an expert on military tactics, but I can recognize a losing battle when I see it! Gotta wonder how that general jerk managed to get into that position despite his stupid tactics."
Deconstructed: The meaningless sacrifice made by the soldiers that refused to retreat creates a terrible scar on the morale of the surviving troops, and the terrible loss of resources during that nefarious day becomes the first piece on a chain of failures that eventually led to the crushing defeat of the heroes at the hands of the evil army.
Reconstructed: Despite facing a hopeless battle, the heroes decide to fight until the very end with all their might and courage. After the tragic end of the battle, and even when they didn't manage to inflict considerable losses on the enemy ranks, the Heroic Sacrifice manages to inspire the surviving heroes and those that were reluctant to stand and defy the enemy.