But isn't that why companies hire employees on visas to begin with? I would venture to guess for every 1 truly pioneering mind that is working in the US on a H1-B visa there are 100 people working on CRUD software at Amazon or Microsoft.
Depends on the company. Companies like Tata and Infosys (which, until recent changes, had something like 80% of H1B quota), sure. Companies like Amazon and Microsoft do not do this as a matter of policy (which is why they sponsor most of their H1B employees for green card); but individual managers are still aware of the kind of leverage this gives them, and some of them try to use it.
They hire employees on visas to build CRUD apps, because it's a seller's market for employees that can pass <arbitrarily high whiteboard interview standards>, and if you're having trouble filling headcount, there's no reason to exclude 7.2 billion people from your hiring pool.