Hype of IITs and IIMs
I feel the entire IIM and IIT scene is over-hyped. I have myself interviewed countless graduates from IIT and their technical capability is no better than those from other colleges.
They are called centers of excellence. By measuring how good and fast someone is at gaining knowledge discovered/created by others, one cannot predict how successful they would be at dealing with new situations, solving real issues.
Working in an industry, we encounter issues which have no precedence, no formula to be applied. Some problems are technical, some are political, some relate to the sheer enormity of the task, some about building a consensus. I don't think the entrance exam would filter correctly candidates which are best of each problem, and for unexpected problems.
If we look are examples the world over, great jobs are often done by people who are least expected to do them. College drop-outs, un-educated, unlearnt people often accomplish great feats.
In addition to that, some people from prestigious institutes have a problem (some, not all). They have a big ego. The behavior of the people at their feat right from their families to all others gives them a sense to superiority over the fact that they have studies in a prestigious institution.
They think those who hail from a not-so-famous institute are less mortals and less capable just because of the fact that they do not hail from IITs or IIMs.
Although not all IIT/IIM graduates suffer from inflated ego, I would prefer hiring in the industry be done on a case by case basis rather than giving a blanket preference to people hailing from some particular institutes.