It's more they're a very limited test of a very specific and narrow range of rather abstract abilities.

Being able to rotate complicated objects in your imagination is more of a freaky talent than a useful one.

Psychologists use a more general concept called 'g', which is short for 'general intelligence' and seems to be almost impossible to test for.

I have a very arbitrary rule of thumb for estimating practical intelligence, which is predictive ability and modelling sophistication.

Given a set of circumstances - which could be emotional, or economic, or scientific - intelligent people are better at guessing what happens next than less intelligent people, even with identical levels of previous experience and knowledge.

Traditional IQ seems to be more interested in abstract symbol manipulations and certain kinds of pattern recognition, and they don't necessarily correlate with prediction and modelling except in very specialised and limited ways.