Why is that we don't stamp papers, books or people?

As per Indian culture, knowledge is sacred and divine. So it must be given respect at all times. In ancient India every subject - academic or spiritual - was considered divine and taught by the guru in the gurukula.

The custom of not stepping on educational tools is a frequent reminder of the high position accorded to knowledge in Indian culture. From an early age, this wisdom fosters in us a deep reverence for books and education. This is also the reason why we worship books, vehicles and instruments once a year on Saraswathi Pooja or Ayudha Pooja day, dedicated to the Goddess of Learning.