I think the H1B process gets abused by body shops. Salaries are pretty demonstrably lower there than at many other tech companies.

At Big Tech almost everyone is normalized into salary bands by level and regardless of what you or your manager does, any discrepancy will eventually decay to level unless you get the formal promotion. They do this very deliberately, because they don't particularly trust their managers and don't want the organization to devolve into sucking up to get a raise. There isn't room for discrimination, and in many cases managers don't know your immigration status anyway (at the one I was at, we weren't supposed to ask, although it often became apparent because employees on visas would have to go home to renew, or they'd have questions about navigating company policies).