It doesn't have to be... and we have Guest Worker programs now.
I don't have any problems with Guest Workers or legal immigrants who play by the rules and pay their own way. I think the threat of asset forfeiture would be a huge disincentive to those who would game our system.
Throw on 5 to 10 years for documentation violations, with permanent sanctions... How's that?
And they have never worked as intended. Too many gamers in the system that find ways to circumvent our immigration laws. If the anchor baby laws were nullified, I'd probably give this idea more consideration but I don't see this ever happening.