This is the Hindu belief that after the death, soul of human being still remain in this materialistic world. Just because of the loss of body (due to death) someone cannot detach himself / herself from this world. The pull of Love, kindness, affection for his / her family, friends, relatives etc. and the affinity for the materialistic world prevent him to go for the extreme and ultimate departure. As a result, being a bodiless state that man (without body) gets pain.
He wants to do many things but cannot. They cannot or even do not want to make themselves free from this materialistic world. 'PINDA DAAN' according to Hindu Belief Gives them an ultimate relief and paves the way for their departure to the ultimate world of Peace. Pind daan is considered to be a mandatory rite believed to bring salvation to the departed souls. An obligation of all Devout Hindus.