The leftist NPR radio explains that it is because of special H-2A visa laws that allow the companies to hire foreigners without paying a competitive wage:
The way Justin Sorrells tells the story it began with a single moment, 17 years ago.That's right, our politicians sold out our workers so that agri-business could save a nickel per box of oranges, and not have to negotiate with workers.
"We were harvesting one of our family groves, with a harvesting crew," Sorrells says, "and directly across the street, there was another grove owner who was having trouble getting labor. So he walked across the street, went to our harvest crew, and offered them a nickel more per box to pick his oranges instead of ours. And the crew did that." ...
"We have been 100 percent H-2A since that day," Sorrells says. "We were the first company in the state of Florida to utilize H-2A labor in citrus." ...
This is one of the biggest criticisms of the guest worker program: that these workers are bound to work for a single employer, and are dependent on that employer for work, housing and transportation for the entire period of the contract. They can choose not to return next year. But for the term of their contract, they're stuck.
Why pay a fair wage when there is a govt-sponsored slavery program?
If you doubt that NPR is leftist-globalist, listen to this story where NPR attacks Denmark for asking migrants to use some of their own money to pay their expenses.