Besides the failed war on drugs and political corruption & drug cartels plaguing Central America, rich white business owners employee undocumented immigrants; illegal immigrants work for less and have no problem doing jobs Americans won't do. For example, many illegal immigrants work do farm work or work for meat packing plants and construction sites.
Once you start putting business owners in jail for breaking the law by hiring illegally, the incentive for coming to America dwindles. Even in Mexico, businesses place ads in papers encouraging immigrants to come to the United States.
It should come as a surprise to no one that employers richly benefit from undocumented workers. Organizations get grants to run daycares for field workers, who they know are undocumented.
I worked for an organization once, when they thought ICE was going to come to the school, the kids remained at home for the week. People are making money off illegal immigration. To be clear: the grants organizations receive for this type of daycares at not taxpayer money.
Regadless of your position on illegal immigration, employers could stop the influx of folks coming to work in the United States by using the free E-Verify system, which allows an employer to figure out whether a person is here legally or not. It also checks on a person's work visa status or temporary work permit.