There is another irony. An article today on FR relates to San Francisco's woes over its homeless/jobless population. Some in city government are trying to do something about it but are getting grief from wacko libs who think people should be allowed to live the way they want.
The MSM/libs cry out about the homeless when a Republican is in office, yet farm work would put money in their pockets, possibly give them an opportunity to better themselves financially, but they're not considered a possible alternative to illegal labor.
There certainly are people available to do the work; they just aren't interested, or the growers as you've pointed out don't seek them out.
Why work when you can get more for doing nothing?! If you are hungry enough you will work!
Farm work is seasonal and you need to get the people to where the work is. After a few weeks, then what?