Why do tools meant for cutting always have sharp edges?

Cutting means the insertion of a thin object all along in a body so that the body gets divided into parts .Tools with thin or sharp edges allows us to concentrate or focus our applied force on less area through which the cutting of the object starts or we can say that the exerted pressure is more in case of thin tools.

Whereas in case of thick tools the applied force gets exerted on a large area and hence the pressure is distributed over a large area so no penetration or insertion of the object happens, hence no cutting appears.