Many countries, including India, are just now getting widespread broadband rollout. Due to its infancy, many ISPs have data caps and may even be delivering data over 4G/LTE to homes. With AMP, Google and CF have the privilege of driving all of this (search-driven) bandwidth to datacenters within the same country, or at least the same continent, to the visitor. If all of this content was really served from the origin, latency would be considerably worse since the data will have to go through the undersea cables and the performance issues that may occur with bad routing.
You could also say the Data Saver web proxy they run is to encourage these users to browse the web without worrying as much about their phone data bill.
Google really wants everyone in these countries to be using and depending on the Internet just as much as Americans use and depend on it, otherwise they may miss out on advertising $$$ potential from a country that's ~4.5 times more populated than the United States.