Only when they don't want to, many stories show cases of yu's understanding the basic idea of "growing your own food", and not necessarily just Yuukas. And they aren't necessarily super smart, just, well, having common sense instead of "shityu sense".
You can say it's more about selfish yukkuri logic trying to claim the world is there to serve them and come out for reasons to demmand service while claiming you're in the wrong for not delivering.
I don't think it's a matter of common sense, smarts or niceness. It's just a defence mechanism gone wrong.
Think about it: yukkuri can die simply because they can't take it easy. Thinking about complicated things or hard work isn't (directly) taking it easy, so why make their own lives harder?
The vegetables were there. The yukkuri ate them. The yukkuri is now taking it easy.
That's all they have to know. Thinking about where the vegetable came from, or knowning that it came from hard work, or worst of all, knowing that the person who did said work will now administer punishment, is not taking it easy. Thinking about that kind of thing is literally worrying themselves sick.
TL;DR: yukkuri logic isn't selfish. It's lazy. The same thing with a different motivation.
The thing is that many yukkuri know that for taking it easy, sometimes they have to work hard, even if it's uneasy, yet it doesn't "make them sick" because they have the concept of "reward in the long term".
Like when they have to hunt for their families, yeah it's uneasy to work extra hard to feed extra mouths, but the easiness they'll feel seeing their little ones happy and well feed makes up for the hard work uneasiness. Hell some even develop the "hard work makes me feel good" mentality that many humans have.
So it's not a defense mechanismn, just an excuse to steal from others and call it rightful, similar to the "hoarding" accusation, it's not about avoiding uneasy feelings, but take away easiness from others.
There is a reason that only the bad yu's do home invasion, farm raids, etc. only they use such selfish logic, good yu's respect the basic ownership idea they have, even if it's for human stuff.
It's all about instinctual habits, arbitrarily decided by beings across the 4th wall. So, as long as you have written story/ankos you'd be right --- <nudge,nudge>
Not necessarily, many of our ideas and views are basically what we gather of the work of others, be it comics or written stories, you don't need to write your own stuff to come out with your own view or to back it up, just recall those works by other yu aficionados.