1) Role models - Kids don't grow up wanting to be a fast bowler because they have no one to look up to. Dev was the best inspiration, and he was a swing bowler. I'm sure that has some relation to the relatively high number of decent (occasionally world-class) swing bowlers India has produced since then. But there aren't any pure pace bowling inspirations, let alone any 'complete' fast bowlers (Wasim, Lillee, Marshall, Steyn, etc) to look up to. Zak and Srinath were good, but never the best in the world. For most of their careers there was talk about fitness issues, lack of effectiveness, being underrated, etc. And they both weren't that quick anyways.
2) Pitches and playing conditions - the pitches in India don't reward bowling quickly. You either cut down on pace and be accurate, or cut down on pace and swing the ball. The Ranji schedule is too brutal for young fast bowlers to maintain their pace, and if that workload doesn't break them, then the international schedule will. There have been so many bowlers over the years who start off young and fast, only to be broken and return as medium pacers bowling cutters and gentle swing. Even school-level cricket schedules are intense from what I hear, but can't be sure on that.
3) Coaching/Selection - Coaches in India coach to earn money. You get more students attending if more of your former students have played for representative teams.
Similarly, selectors/coaches of representative teams pick players to win trophies. Not to develop them. Young tearaway quicks on dead pitches who break down after one game do not win competitions. Accurate, reliable medium pacers who can cash in on grasstops, or hold up an end while the spinners work away, and who can play for the whole season are far more desirable. They get picked over young, erratic, fragile fast bowlers.
As a result of such selection policies, bowlers are told to focus on line and length and variations when they are young, not pace. I have witnessed this first hand. Young spinners are told to try and spin the ball, young fast bowlers are told to bowl line and length.
The coaches take young talent, and mold them into players who will get picked for the representative teams, which in turn are trying to win games in competitions and on tracks that do not encourage fast bowlers. It's a vicious circle, that is made worse by the fact that since there are no Indian fast bowlers setting the world alight, there is a continued lack of role models, and a continued shortage of youngsters with a desire to bowl fast.
Indian culture plays a role too - Parents/Teachers/Coaches all generally raise kids to win and perform, in every single aspect. Education, Career and Sports. This mentality makes kids more obsessed with short-term success (getting picked for the school team, the uni team, the A team) rather than lofty long-term ambitions (being India's first ATG fast bowler), and they are more inclined to do what it takes to meet the arbitrary criteria of success set for them by their elders. It's a massive flaw in our education system too - the way we teach and assess kids in India means they study hard with the aim of achieving high grades, and not to actually learn anything. This seems to have seeped into our Cricket system. Young kids will do whatever their coaches and say and make sure they tick all the boxes in order to get selected for the next level, and won't risk being a eccentric, different, unorthodox cricketer if it means failure.
In contrast to this - Pakistan have a stronger culture of pace bowling, coaches/selectors who love quick bowlers, and less intense grass root cricket schedules, which allow for these young quicks to grow. Pakistani culture has also diverged from Indian culture in a sense that, possibly due to the political/social situation in the country, people seem to pay more attention to having fun and doing thing is a more stylish, artistic way than they do to purely achieving results.
The diet and genetics arguments are nonsense IMO. They vary so much across India itself, I(the average Punjabi or Pathan kid is probably as strong and fit as the average black/white one and just as capable of bowling quick) and the argument will only apply to the general population as a whole. We are talking International level cricket, and elite few cricketers out of the country of 800 million. It is definitely possible to find a handful of kids with the physique to bowl fast in India.
My source: Grew up playing cricket with Indians and Pakistanis in Dubai. Was coached by an Indian coaches. It's shocking how, despite the fact that we grew up in the same country, with the same facilities and tournaments and the same diets, all the fast bowlers were inevitably Pakistani (or Sri Lankan, oddly enough).
Point 2 is from a nice article Akash Chopra wrote on this same topic, I'll dig it up later.
