There is a difference between culling low performers and culling high performers in an org or team that's no longer wanted.
Most layoffs don't just fire low performers. They fire people working on products that turn out to have no future.
I find this especially sad. An individual through no fault of their own could be easily laid off just because of being on the wrong team. In contrast an individual performing unsatisfactorily could not easily be fired (i.e. for cause).
Cull the bottom 10% takes a very long time (and effort) in a big company.
You still have to put the "candidate" on PIP, wait 6 months for the PIP to fail, then run the ejection process (ranging from 0-2 weeks in the US to a few months in EU).
and you have to sacrifice a senior eng to mentor the PIP'ed (else they can sue you for not giving them a fair shot).
The whole thing is much more expensive and slow than a company-wide layoff.
In fact, don't many of the Megacorp companies have a 'cull the bottom 10% annually' policy anyway?