Probably because most stabby blows are going to come at an upward or horizontal angle, less from the top down at an angle that could penetrate. Holding a pointy weapon above your head and driving it down at close range exposes your torso. You could use a halberd or billhook for a top-down strike, but that’s still not super likely to be at the right angle to slide between the pieces. Longer weapons like that were used more for poking than swinging like an axe anyway.
This was my thought. The way the center line is angled it looks like they want thrusts to hopefully deflect away from your neck and up and over your shoulders.
Probably because most stabby blows are going to come at an upward or horizontal angle, less from the top down at an angle that could penetrate. Holding a pointy weapon above your head and driving it down at close range exposes your torso. You could use a halberd or billhook for a top-down strike, but that’s still not super likely to be at the right angle to slide between the pieces. Longer weapons like that were used more for poking than swinging like an axe anyway.
This was my thought. The way the center line is angled it looks like they want thrusts to hopefully deflect away from your neck and up and over your shoulders.
Just a guess though.