Rebirth and rituals for the departed

Hinduism believes that the departed souls are reborn sooner or later.  There’s no way of knowing when it was reborn. Yet rituals are continued to be performed for the peace of the souls. Since Hinduism believes this, then why is puja performed for generations for ancestors?
Does no one want to educate people about this? The new generation asks questions. What is the answer to this question?

We are here as a result of our ancestors sacrifice and love and caring etc. We honour and respect the heritage from which we came.
Every culture in someway pay respect and homage to their departed ancestors, Chinese, Japanese, Native Indians, and even the westerners. Westerners do this by visiting the graves and laying wreaths or flowers. In a more elaborate way other cultures pay homage to the departed.
Hindus in paying homage remembers the departed and symbolically offers prayers to the Infinite Being to bless and convey our offerings to the departed starting from the creator of this universe.
We give thanks and remember the departed because it is through them that we are here.
It does not matter where the Jiv Atma is, liberated to become the Atma  (soul) free from all attachments and becoming merged with the infinite again or still on the journey to this goal, we are grateful to the line from which we have come and therefore we pray and thank them and pledge to carry the torch forward.
Answered by Robin Doobay on April 16, 2016