You see, I do kind of get the rationale. Here's why:

1. Edible and good batch comes out sub-standard
2. Employee asks supervisor about keeping it
3. Supervisor agrees
4. Employee tells other employees who help produce the batch that sub-standard batches can be saved
5. Other employees ask about splitting the batch
6. Original employee agrees
7. Employees who help produce batches propose "messing up" on some future batches because it'd be cool to get some free product
8. Original employees agrees that'd definitely be cool, and will ask the supervisor on the next ones as well
9. More sub-standard batches are produced
10. Employee asks to keep them
11. Supervisor agrees
12. More batches are getting split
13. More employees realize, "f*ck it, we're getting away with pumping out substandard batches occasionally, let's do it more often"
14. Even more sub-standard batches are produced
15. Employee doesn't even have to ask at this point because it's normal for sub-standard batches to be taken by employees
16. Supervisor looks at numbers and realizes quality output is declining
17. Goes back to old policy
18. Output "somehow" improves again
19. Leadership sees the pattern
20. Supervisor gets fired

I've worked at many places and know all too well how common it is for people at jobs to take liberties anywhere they can be had. So many things at different jobs I've worked were getting stolen all the time. Never underestimate people's ability to find and leverage an exploit.

And so the businesses know it's just better to avoid any potential exploits by disallowing for loss to be retained by employees.