The Democrats want illegals to stay and become Dim voters. The Republicans have been told by their owners that the US needs cheap labor (see GWB above). Both of them see illegal immigration as something that needs to be legalized. Trump saw it as something we need to stop. He got elected.
Bingo! A lot of people would take on these seasonal jobs if it didn’t mean they’d lose state benefits they actually need. The welfare system is structured to keep people down ):