Question

why is the one end of drawing pin kept wide, but the other end very sharp ?

Answer 1

one end of drawing pin is kept sharp so that it can Pierce the drawing board as more pressure will be applied since pressure is inversely proportional to area.
the other end is kept broad so that we can press the pin with ease and the pin should not pierce in our hand

Answer 2

Because if one end is very sharp then area is less and there will be more pressure .So the pin will enter into the object easily .The another end is kept wide because if it is hitted by a hammer then the pin will not enter into the hammer easily .This is because area is large and pressure is less.