The chisel tip is useful for food preparation, particularly for fish. I don't know if it was historically designed for this purpose or not, but if you get your hands on a chisel-tipped sushi knife you'll find out exactly what to use it for.
I know that there were armor-piercing kissaki designs from feudal Japan that were shorter and less integral with the rest of the cutting edge. But I don't recall ever seeing a traditional kissaki that was a completely separate cutting edge, like modern chisel tip designs. So while I can say it may serve as an "armor piercing" design feature I don't know if that concept was ever battle tested and compared with other kissaki types for efficiency and effectiveness.