Why is Saraswati Puja celebrated?

Aum Sai Ram.

Q. Why is Saraswati Puja celebrated?
A. To acknowledge the passing on of ancient knowledge.

Q. What is ancient knowledge?
A. The knowledge of the inner and outer universe.

Q. When it all started?
A. It always existed in the form of Nada (Sound).

Q. Who discovered it?
A. Lord Brahma.

Q. Who reformed it as discernible truth?
A. Saraswati as Vaakvaadini (Divine Speech).

Q. Who recorded it?
A. The Rishis in the form of Vedas.

Q. So what is the meaning behind the rituals?
A. To offer back to all the ones, as a mark of gratitude, who had primarily offered to us.

Q. Which will be?
A. To place books, instruments, tools of knowledge etc., in front of Goddess Saraswati, beseeching to be blessed with correct understanding of it, as it was once revealed.

Q. Ah! Now it is beginning to make sense.
A. It was never a nonsense. It was your comprehension of the meaning that wasn't making sense to you.

Q. Thank you!
A. No. Thank Her by respecting the expressions of knowledge.

-- Article Courtesy:
Srinath Raghavan.