It is overwhelming obvious why product development for Creo Simulate is performed in India. PTC can pay developers in India a fraction of the cost of what they would have to pay developers in the USA.
I think all of Windchill is developed in India, as this was explained to me at the recent PTC Live event in Nashville, TN, from someone from India who works with Windchill and other PTC employees.
All of the licensing support for Creo is also in India.