It’s also because scientific ethics committees veto these kinds of studies. I’m not sure if this is just my uni but we call them “pandora’s box-studies”, meaning studies that could lead to a massive amount of unknown consequences, so in this case they veto it because they know that people will cite the study as a justification for racist behaviour.
The few basic studies that have been done do indicate some kind of biological difference between races, which makes sense considering humans have lived and evolved in very different environments, but this research was deliberately written in a very dense and user-unfriendly manner because they didn’t want to have to deal with any racist tomfuckery. Now it’s just not worth it. You might find out that one race has slightly is slightly more suited to a certain environment than another, and all you’ll really get out of it is some incredibly racist behaviour from degenerates who would see this as definitive evidence that their race is superior.
Hopefully one day this very sensitive field will be accessible to science because it would be fascinating to see what differences there are and what causes them, but people need to grow the fuck up first.