'Upgradation' not universally accepted?

It is a word that has become established in one variety of English (Indian) but is more or less unknown in other dialects of English. That is really all that can be said.

It's an informal word created by informal English users who collectively influence large group of users/people. Most of these words originated from India (eg. upgradation, updation). Basically, it is used by English users (Indians) confidently thus influencing the other non-familiar English user that it is a formal word. With India's population these words had become common through the years. Nevertheless, these words are not formally acceptable to native English users.