Question

why do tools meant for cutting always having sharp edges

Answer 1

Tools are made sharp because with less pressure we can cut things easily.The pressure falls on small surface area so no great pressure is needed.

Answer 2

the tools for cutting always had sharp edges because when the area of edge will be smaller then it will put a more pressure on that object to which we want to cut.
for eg. knife , as it has a thin and small edge it will produce more pressure on the object.