To have left hand and right hand of Kiridashi are ideal way of curving wood, because when the bevel side is attached on the wood block, the blade moves away from the wood surface. I meant what the blade bites smaller amount of wood surface, and slip away. It is great for when we need to remove tiny amount of the surface of the wood that is something like clean up little bit. That is happens to the single bevel edge blade.
In the other hand, when we attach the flat concave side on the surface of the wood, it bits the wood, and the edge is going to deeper side. It is great for when we need to remove lots of meat of the wood. Therefore, if we have the left and right hand kiridashi, we are able to use them more occasions.