The work done with devotion (shraadh) is known as shraadh. There is also a sunray called as shraadh which rises at noon and provides elements essential for life to human beings and living beings conduct jaap, pooja (worship), anushthan, shraadh etc.. to provide power to that sunray. That's why there is the tradition of conducting Shraadh in afternoon. Therefore as various necessities are required for survival similarly shraadh is essential for satisfaction of ancestors (pitra).Ancestors being satisfied by the Shraadh ceremony, bestows their blessings on their heirs in forms of happiness and propriety.
In Indian Hindu culture three kinds of Shraadh has been described .
They are PITRA RIN, DEV RIN and RISHI RIN .
Different time and procedure has been determined for the human being to get relief from all the above stated RINS.
But in today's scientific era ,due to polluted contemplations ,the human being are getting far away from all these activites which leads to
various adverse consequences in form of pain ,sorrow, failures etc..Though pooja ,vrat (fasting)etc.
human being satisfies the devrin. PITRARIN are satisfied though Shraadh etc. hence these ceremonies must be performed.