IMHO, with a billion people, I believe that BOTH a) your generalization is true, i.e., the majority is disinterested AND b) not relevant w.r.t. Olympic medal-winning potential : it is enough for a small minority to be interested in sport / fitness & glory to make the cut for the olympics. I believe that the 80/20 rule applies, and is actually more of a 95/5 rule in most societies and most achievements : 5% of the population account for the glory (, the rest just wake the flag and feel proud, conveniently forgetting that one cannot be proud of what one did not achieve
personally).
I suspect you might find a similar proportion of everday Chinese equally disinterested in "poses" (not sure, just speculation).
I believe that the core reason is our usual friend, corruption and red tape. It's not just sports; in general, the meritocratic lose out because wherever there is an opportunity in India, whatever be the form of opportunity. That includes what is rightfully yours, such as welfare handouts, your passport, etc; An Indian's everyday life consists of jumping through hoops to get basic things done.
Disclaimer : am Indian.