The worst I've seen was where I had to do 100 questions and half were spatial intelligence (gameable and wtf). It looked like an incredibly expensive piece of software. Didn't get the job, thankfully, but the company's now known for having a policy of not being able to talk about work out loud if you're in IT. The other places that gave me tests had dissimilar, but equally insane workplace policies.
-At some level, the person interviewing you (or management) doesn't trust their intuition to find the right candidate.
-It's an easy way to throw someone out of a pool despite all else. There's a reason it's illegal to do IQ tests.
-Mental health issues such as dyslexia or ADD.
-I've taken maybe five intelligence tests for work and none of them have been the same. Where's the standard?
-Companies have a weird tendency to use puzzles such as the "three light bulbs" one. All that does is test if you've heard it before. "I want to see how you think" makes no sense when the question's on paper and there's 100 questions just like it.
-A lot of these tests are gameable since you can just practice beforehand.
-Test anxiety sucks.