If you look at it from the point of view of charities, they might prefer getting a lump sum donation in big amounts rather than a lot of small contributions. First it is less of a hassle. Second, knowing that they have this certain big amount with them, will help them aim for more ambitious causes and plan better.

And don't worry about salaries in India. I can tell you that most of the people whom Google or similar companies can pay here, are already well paid and have sufficient disposable incomes for contributing to charities if they so wish.