There are all kinds of reasons, with a long history. Small businesses are getting other aid. But the small businesses depend on the labor of many of those undocumented workers.
In the UK, where anti-immigrant sentiment is very high, and they effectively have barred all Romanian labor - they've quietly (almost secretly) had to import thousands of Romanians, to work for very little money, or else their fruit isn't getting picked. Thousands of bushels of fruit crops have wasted. England has a real problem right now with food security, for obvious reasons.
So these lucky Romanians get to pack onto a plane, during a pandemic, be transported to low quality housing, work long hours, and get sent home with a check.
We don't do that in California. We did it a long time ago (google the Bracero Program) and it didn't work. It was so hard on the children of the families (unlike UK, we don't fly people in - they come across land). We're not. big into family separation in California. Most of us believe that all workers should be treated with dignity
So, since we need fruit pickers here (badly) and we export enough produce from California to feed several other states, it's important that even those these workers do not meed federal standards for entering the US, we have them here.
They are small in number. They are permitted to send their kids to school. They have to be vaccinated to go to school, just like everyone else. We know where they live, they have to provide utility bills or housing contract to go to school. That way, health improves and criminality is reduced.
So don't worry about how California is doing it. We've got an economy that recognizess all essential workers.
I'm listening to Gov Newsom's live conference right now. He is talking about how in our second list of objectives, we have to secure our food supply. It's picking season for many crops, and it's also packing season so that people outside of the Central Valley and outside of California can get food - that may include some of you here on WS.
We produce almost all your almond milk, for example. Shelf stable and fresh alike. Many of those workers are undocumented because the federal government doesn't think they qualify to be "essential." But no one else will pick almonds. So California officially regards them as essential and treats them as essential.
Strawberries, lemons, limes, oranges, avocados, tangerines are all going from field to market right now. We hear the lemon trains every morning. The workers at the lemonade/lemon juice plant are about 10% undocumented, the rest are legal residents. Right now, that plant is shut down and soon the refrigerators will be full, so Gov Newsom is authorizing food production workers to go back to work, with a specific social distancing plan (and masks).
Personally, I like citrus. I can live without strawberries. Lots of people get frozen strawberries, apparently. If that industry fails, I'm not sure the owners have the means to restart easily - eventually, sure. But no rancher I know is making huge money, they are making an okay living, the workers (documented or not) get $15 an hour, but that doesn't go far in California. With 4 wage earners in a household, though, it's a good living - and that's how most agricultural workers live. It's worse in most other states.