Pretty sure layoffs decrease productivity of the remaining employees, unless you're a H-1B visa worker, no one "works harder" after layoffs. Morale is low, resentment over "now I have to do X as well" grows and productivity gets hit.
The company is signaling that it is not doing well - why shouldn't I leave for a company that is doing well?
The only way I'll stay is if you want me to be part of a real plan to turn things around. And my involvement in that has to be rewarded - not just at the successful end of that process, but immediately.
That employee now doing extra work accepts it because they are either scared of being laid off themselves, know they can't find a better job elsewhere, have irrational loyalty to the company, whatever. In any case the company benefits by exploiting the person.
If instead the person leaves, then the process fails and the issue rolls up the org hierarchy. Now the leadership evaluates if this process was actually necessary anyway. If not, let it die or let the shit roll downhill elsewhere. If it was important, invest in the refactor that everyone knew was probably necessary anyway.
For corporate leadership it's an easy way to either squeeze more out of the peasants, or force a reevaluation of priorities.