The shaft and tines of the sai were used to block, strike and ensnare enemy weapons. The shaft of the weapon was never bladed , which would have made any reversing action in order to strike with the hilt, or block with the shaft, along the forearm, completely impossible. If the sai were used for thrusting to any depth into the enemy's body, because of suction it would be very difficult to withdraw the weapon, which would render it useless. This may be another reason why an extra sai was carried. Many of the weapons kata from the Ryukyu Islands were named after their founder, or their place of origin, and have been passed down to modern times. -Michael Finn, Martial Arts: A Complete Illustrated History, The Overlook Press, 1988
Why would you want bladed Sai?
The angry man will defeat himself in battle, as well as in life. -Samurai maxim