If one is not able to reach his peak potential, then his own problem and not an IQ measurement deficiency. I'll read the IQ value that you're able to reach, not the value that you might reach potentially if you make an effort.

Being able to reach your peak IQ potential consistently is part of the daily hygiene of eating well, sleeping well, exercising well. And it's also a question of making the effort. If I can't measure it, it means you don't reach it. Or at least not often enough.

On the other hand, I agree that it might be overstated. But having worked with people that don't have the best minds, you start to believe IQ is not just crap.