Because making any decision about an unborn child should be based purely on the medical needs of the child and if applicable the mother. Selecting based on traits is eugenics and I hope I don’t need to explain why that is bad. But as I understand the reason Musk is having all these babies is because he totally believes in eugenics, which is terrible.
Edit: just checked, in most of Europe this is very illegal. Gender selection is only allowed if there are strong medical reasons to do so. For example a hereditary disease in the family which only affects one sex and can’t be screened for in another way.
People Can’t Memorize Computer Industry Acronyms