Outsourcing has proved to be the hallmark of global development and has increased the footprint of companies across the world. There are many benefits associated with outsourcing such as -

Significant Cost Savings - Companies can save 30-50% compared to the cost of a U.S.-based employee for the same level of performance. Infrastructure costs in India and other developing nations are lower thus saving significantly on capital.  
Access to Specialized Services: The function that a company outsources may not be their core competency but they can find an outsourcing partner who is specialized in that particular business process. A company can seek services from the most cost effective and specialized service provider.
Time-Zone Advantage: The offshore teams usually work during the night hours in the US, and that gives a 24 hour work cycle advantage to the US clients. The combination of US and offshore teams ensures a much faster delivery cycle.
Reduction of Legal Exposure - Employee issues can be time-consuming and can escalate into legal liabilities. Using offshore staff eliminates certain legal exposure to employment liabilities.
Flexibility - Unlike traditional employee relationships, off shoring eliminates hiring and termination costs, allowing companies to quickly expand and contract their overseas staff in accordance with business needs.
Retention and Loyalty - Many times companies are rewarded with higher levels of retention and loyalty from offshore staff because overseas employees typically consider working for an American company to be prestigious.