People have an intense fear of this sort of thing. It is very deeply wired into our brains to worry about threats from people who are alien to us, and who are also potentially stronger. So if you’re going to make an army of super-human soldiers (or even just citizens) you’d better be sure their performance is so much better that it’s worth alienating every other person on Earth. Given that warfare seems to be moving in the direction of autonomous machines, it’s a little bit difficult to imagine that anybody is going to get a lot of benefit out of this sort of thing, but who knows.