Whenever I discuss IQ with Tracy she says something like, "of course some people are brighter than others, but what's the point of measuring it? Why tell people that they're superior?" Well, here's why. Being able to determine a persons intelligence or other attributes should work to the advantage of the stupidest and laziest. Imagine in the future it will be possible to directly test for intelligence, laziness or susceptibility to alcoholism via a brain scan or something (and to predict the probability of your future child suffering from them). Parents could then insure their kids against stupidity. I'm not talking about the kind of stupidity and laziness that I suffer from, I mean the more serious kind. This blog post suggests that homeless people in America often have an extreme lack of conscientiousness rather than victims of gross injustice.
This insurance would only work if these qualities have a large genetic part otherwise it would be too easy to game the system. So if genes are very important it is easier for the unlucky people to cash in.
There are other ways it is better. It's nice to be tall, beautiful and clever, but being tall is not an achievement and is nothing to be proud of. The same thing goes for intelligence, it's just luck. We all figure out pretty quickly who's good at what at school and by overemphasizing the role of hard work in success we encourage talented people to feel morally superior in a way they're not.
The nurture side encourages us to look for bad parents or lazy students where there aren't any. Sometimes there isn't anybody to blame.
Also, making it more expensive for parents to insure high risk kids would be like a non-coercive eugenics as people on the margin chose not to have those kids. This could have big long term effects by (slightly) counteracting the evolutionary effects of people with genetic defects (things like poor eyesight) being able successfully reproduce for the first time ever.