Because we are fed up of mourning over nothing.
Because people die, grandfathers die, and the real mystery is to see a strong personality, which represented a wall in the whole mansion of your life, pass away, suddenly disappear, come back to nothing.
People grow and root themselves in this world, and then suddenly leave.
We are not eternal, and this conscience and awareness which accompany us in the world, is to be swept soon.
Consequently, thought about giving oneself death, or the feeling of absurdity facing the desappearing of someone, is a sympthom that we are out of place.