It's true that these institutes haven't started something revolutionary, but there has been considerable amount of work in the right direction. I think there are multiple possible reasons behind it: 1) Most of the undergraduate students from these institutes either go study abroad or take up a job; which leaves only a fraction of the top students in these institutes. 2) Students who come for MS in these institutes have to clear GATE exam and most of them, according to what I have seen, join these institutes just for getting a good job and not for serious research.

Disclaimer: I work at one of the top institutes you mentioned.