Your point actually makes H1B worse than "indentured servitude" of the past. Many (if not most) H1B folks stick around at one company just waiting for a green card. This kind-of means it is involuntary in some sense. However, unlike indentured servitude, there the "young person" does not automatically get a green card and is not "free to leave" at the end by default. By default, at the end, he/she has to leave the US.