There have been allegations in the past that political parties in India have rigged EVMs and I think that is quite likely despite the lack of "evidence". To understand that, you need to know how the voting system works in Indian elections.
The educated elite in India are apathetic to voting. They have no trust in the administrative system and have no hope that the endemic corruption will ever end. So come election time, the people who vote are mostly the poor who hope that some day, the extravagant promises made by the political parties will be kept . Before election day, the voters are bribed with free liquor and food. The women folk are given new clothes. And finally cash is also distributed to bias the voters to chose a particular candidate. The system which issues voter identification cards is broken and sometimes you can find impostors voting on behalf of actual voters.
Given the amount of money that politicians spend on rigging manual voting, tampering EVMs is just good business practice. It is cheaper and you don't need to chase around thousands of voters.