Why is the cutting edge of the knife is made sharp?

There's two basic types of quality chef's knives: Japanese, very hard steel blades, and German high quality steel blades. Handle designs are simply a matter of individual preference. The Japanese steel is more difficult to sharpen, but once sharpened, it maintains its edge longer. These blades are usually sharpened with a razor edge, a 16-1/2° angle on either side of the edge. The German steel blades are usually sharpened with a 22-1/2° angle on either side of the edge. Both knives can be very useful in the kitchen. The German knives might be described as more rugged than the Japanese knives...not always the best for cutting sushi, for instance. The Japanese knives typically have thinner and more brittle blades. I own both and I love both. I simply use one for general kitchen work, and the other for delicate, close and precise work.