Back in the old days, the US didnt need scads of people to cross the border to work in the food industry, construction and other relatively unskilled labor jobs.
This all evolved because businesses could get these people to eagerly accept minimum wage jobs and be reliable and somewhat exploitable due to their illegal status. But the real driver was the mismanagement of the country they left. Only desperate people risk life and limb for a minimum wage job. But this was all acceptable when times were good, now the reverse is at hand.