Question

why all the cutting instruments have sharp point

Answer 1

:-less area gives more pressure(that's why we use pointed pin wall)
:-more area gives less pressure.(bag stripes,blunt knife of jam)

Answer 2

Helloo!!

the edgell of the cutting tools is very sharp to reduce pressure.
this results in action of large force over a small area which is in contact with the sharp edge
so the pressure increases and cutting becomes easy.

hope it helps