I don't know about Infosys, but we have a TCS (Tata Consultancy Services) branch here in Uruguay, and it is very common for junior developers to do a few years there, and then quickly realize they've "outgrown" the company and get recruited somewhere else or start their own company - and those "child" companies recruit the cream of the remaining crop, leaving the worse/less motivated employees at the mother company.

TCS does try to keep some of the better ones around, but from the outside I cannot know how succesful they are.

And that is the reason why there is a mass of underpaid talents.

It's definitely possible that the blue-chip companies are missing an opportunity to develop talent out of that ecosystem, but it's also not their responsibility to do so. Most of us who are senior engineers at whichever high-flying company were, at one point, just working on some boring-ass webapp.