1. These guys have worked pretty hard and/or are pretty damned smart which was the reason they got in there in the first place. The placement opportunities reflect exactly that and that is a pretty strong incentive for them not to launch their own startup.
2. Getting some working experience is a very good thing because their jobs offer them great exposure and experience, a pretty strong network of people and a clearer picture of what they are up against. While jumping off a cliff might be very brave and fashionable thing to do, it might not always be the smartest.
The startup ecosystem sucks in India and is nothing compared to the US (I leave room for the grass is greener effect - I don't think that is the case here). Funding is hard to come by and most business don't like dealing with startups. When the odds are that badly stacked against you, a broader network of people helps enormously.
3. A good %age are gasp actually interested in their engineering courses (IITM particularly has a healthy number & tradition) and pursue further studies abroad. A few of them go on to start their own companies in the US and others contribute to startups there.
4. When I see the word solution, I expect to actually see a solution - not read why you think it is an inherent quality.
5. Never use statements like "X group never does it". It takes away whatever miniscule credibility the article has. Some obvious examples of IITians doing startups: Flipkart, Rabi Kisku entertainment (Rabi Kisku and Siddharth Nuni are about to release their movie Software Hardware kya yaaroon) and several several more. You just have to look.
6. Startups are not for everyone. Hardworking and smart alone doesn't cut it and it is not a bad thing that not all these guys are doing it. Doesn't mean they are wasting their life away.
Disclaimer: I was one of those Vetti 5 pointers at IITM, who took a 2.75l job in 2006 ago and I am running my own bootstrapped startup with my batchmate since 2011. If my startup fails (at my last stand), I don't think I will do a bootstrapped startup in India ever again and that has very little to do with the size of my cojones.