For the same reason why they made the Myoboku Oils recharge/spend only (which they technically are still.....barely redeemable...or in very limited supply). Its for the almighty dollar. They will drag it out for a month before they start doing decent redeems or shop updates. I mean, just look how its priced in the balloon event. 800 points just to get 40? You will barely get 400-500 points with the 77 shuriken as it is.

Hope that answers it for ya.