H1B is not immigration. It’s a temporary work permit based that can be revoked at any time by your employer firing you.

H-1b is not an immigrant visa but, because it is dual intent, it is frequently used as a part of the path to immigration but would-be immigrants, and the fact that H-1b immigrants disproportionately come from places where immigrant work- and family-based visas have long wait lists because of per-country caps has a positive feedback relationship with this, both contributing to it and being reinforced by it.