It's a visa. The whole point is that it's not permanent and you are ultimately expected to return home permanently. You may also be asked to leave at any time. It's reasonable for the host nation to want to ensure that outcome is still available and that someone hasn't actually fully emigrated here with no options for return.
Ultimately it's known to anyone who applies for a visa that this will be the requirement, and so, if they don't want the economic opportunity of working in the US, they're free to avoid the stress and just stay in their home nation.
> It's a visa. The whole point is that it's not permanent and you are ultimately expected to return home permanently
probably do not have to tell you this but not all visas are created equal... this one is particular is a dual-intent visa so what you are saying applies to SOME visas, just not this one :)
Ultimately it's known to anyone who applies for a visa that this will be the requirement, and so, if they don't want the economic opportunity of working in the US, they're free to avoid the stress and just stay in their home nation.