The main reason for that is the structure of Indian Institutes, The top Universities in USA or UK offers everything science, tech humanities,law, research output and jobs. The top Indian Institutes on the other hand are subject focused. IITs focus mainly on tech and somewhat science. They also are more research oriented than jobs. IISC and TIFR on the other hand are complete research foucused. ISI tries to balance the two, but offer very few courses. Their humanities departments are also weak. The total output is already top 100 level. As I have mentioned before, in Nature's research ranking 5 Indian cities are in top 200, with Kolkata, Bangalore and Mumbai in top 100. But they are divided into different schools.