Why is this extreme "nurture over nature", "blank-slate" mentality not applied to any other disparities in biological expression save for the brain/intellect?

Why is this extreme "nurture over nature", "blank-slate" mentality not applied to any other disparities in biological expression save for the brain/intellect? Do we all think that, say, the massive racial disparities in 100m Olympic sprinters, or NBA basketball, is due to "practice" "culture" and "work ethic" primarily rather than genetic/biological factors of physical ability? Are say a group of 5'8" Asians going to have the same potential ability to play top level basketball compared to a group of 6'8" Blacks? Does practicing change this dominant variable? Is the differentials in height due to "culture" or "biology"? Is it not common sense that people have a natural range of potential ability for certain things that are biologically constrained, and practice and effort can shift ones ability within this range but not change the biological constraint to where this range lies? Why does evolution and natural selection stop at the neck? Is the brain not also a part of the body, made up of the same organic material? And finally, is "work ethic", "culture", "attitude", "affinity for intellectual focus/interests" 0% biological/heritable? Is that not also partially genetic along with the natural potential? Not that this is definitive for one individual to another, but in aggregate group averages bear this out statistically over long periods of time in different locations. Let's take a step back and just think about the obvious here: how many "hackers" here on hacker news can say they did fairly well on the SAT and standardized tests, above average or well above average, and didn't prepare much at all? Whose parents didn't put much effort at all into pushing them to study for it? I'm sure quite a bit. Is that not an example of natural ability, nature, dominating over nurture? Not that they couldn't have done a bit better if they had, but that their cognitive potential to do well on these tests, to a significant degree was biologically determined? To deny this is similar to the myth that everyone can pull themselves up by the bootstraps. No, often one's inheritance, monetary or biological, have some say in this.