[thesumofall]

Because it is really hard to reliably hire good people. Almost all typical signals & methods (CVs, experience based interviews, …) have very low reliability. An IQ test has the highest reliability according to studies but would be illegal in most jurisdictions. Plus, hiring managers frequently don’t know what they want or they believe they want something that they actually don’t

[tptacek]

IQ tests in employment are not illegal. This is an Internet myth. Several large corporations (with deep pockets for employment lawyers to go after) openly use them.

The reason more companies don't use IQ tests in candidate qualification is that they don't work well.

[prepend]

Where is an IQ test illegal? I remember taking one for my first job in Florida, but the company stopped because it wasn’t a useful signal.

IQ is correlated to many things (eg, income) but I’m not sure about job performance. Maybe for some industries. I was working for a software company and it seemed pretty useless for hiring or selecting project team members.