Outside of a fascination with Intellectual Supremacism, why are people so obsessed with the genetic basis of IQ scores?

Presumably one could do similar identical twin studies on half-marathon race times and SAT test scores. Does no one bother with those, because widespread awareness of half-marathon training regimens and SAT prep courses would spoil the (desired) illusion of some "innate superiority of blood" being measured?

How about the fact that the human mind and genetics are simply fascinating and interesting topics. I would imagine that people don't care as much about running and high school testing because they are fairly niche interests relative to abstract thinking in general, something that almost everyone spends much of their life doing.

There are many reasons. For example, there are large policy implications for schooling and education.

because then for the health of your offspring it's all determined by the wife you choose

but you can choose any wife and put it in an expensive school, be my guest!

Exactly, it is on of the least remarkable results that intelligence is partly heritable. Obviously intelligence is partly genetic, obviously your ability to run a marathon is also partly genetic. Why one has devolved into a bizarre case where so much effort is spent on the minute details of this question and the other is accepted basically as completely uncontroversial (given who is currently competing for top times at marathons it is basically inarguable) is very strange.