I work at a company where performing a RIF is the most common way to get rid of people who are not performing at their expected level of effectiveness - the company does not have any meaningful process internally to perform performance reviews under normal circumstances, but its 'known' even by non-management types, who is effective and efficient at their job, and who is not.
If you aren't measuring performance than it doesn't exist and doesn't matter. So all you have to rely on what it looks like and personal biases. Most companies don't want to or can't do the leg work for a legally compliant performance related firing. It's easier to bundle everyone into a giant RIF.
The downside is the bad performers and the good performers don't get valuable feedback. Good workers assume they are in the former group which feeds their paranoia.
Not all jobs can performance be measured in concrete statistics.
We've had some really likable good guys who just couldn't keep up either technically or functionally, and it's obvious to everyone around, even if no deadlines are missed, and margins are met.
