FSK: If you pass on many good candidates, and you have a small chance of hiring any given bad candidate, then each good candidate you reject actually INCREASES your odds of making a bad hire.
Idiot: We made a bad hire once! Never again! Now we reject lots of good candidates to avoid that repeat disaster!
FSK: But, if you want to minimize your bad hire rate, you also have to minimize the number of good candidates you reject.
Idiot: NO! NO! NO! The way you make sure you hire no bad candidates is to be so strict that you reject lots of good ones! That's what everyone told me so it must be right!
In one ear and out the other. Why do people who don't understand statistics get to be managers? If you don't understand this statistics argument I made, you're unqualified to work in any sort of technical area.
Hiring a good employee is not nearly as impactful as hiring a bad one. If you can have a strategy that filters out 100% of bad employees, but unfortunately also filters out 90% of good employees, this is preferable to filtering only 50% of good employees, but also only filtering 90% of bad employees. You may have more good employees with the latter strategy, but the bad employees can kill the team.
Firms are hierarchy-based entities. "Technical Merit" is about a third or fourth order away from what really drives the hiring decision. Its also very imperfect predictor of actual performance.
The issues is that companies use the term all the time. They want people to believe they were hired for their merit, but merit is almost always 'fit' and not technical in nature. The technical hoops are just a CYA for when the 'fit' doesn't work out (mis-judgement) and they need something to point to as to that is not arbitrary in nature to explain how other people were not hired instead.
Whether or not this actually reduces the number of bad hires is beside the point. It's a classic principle-agent problem.
They fear they might be bad candidates. They'd rather reject too many than too few, so they make sure they reject everybody who they're not 100% is a good candidate. That means they may reject some good candidates that aren't easily identified as such, but it doesn't increase their chance of hiring a bad candidate; it decreases it.