Humans and soul beasts had different physical structures. Humans had three locations where they could condense and store soul cores, while soul beasts had only two.
Soul beasts could only condense soul cores through the more difficult method of Yin-Yang Complementarity, while humans could choose another method called Isotopic Resonance. Thus far, every Limit Douluo in human history had used this method to condense their soul cores.
No, rather than saying nobody had condensed yin-yang complementary twin soul cores, it would be more accurate to say that humans currently had no method for doing so. Without even a method, naturally, few would choose a path that required building the stage from scratch.
More importantly, humans lacked the physical constitution of soul beasts. It was practically impossible for them to withstand yin-yang complementary twin soul cores.
As of now, the only soul beasts in the world with yin-yang complementary twin soul cores were Di Tian and the Evil Eye Tyrant. Di Tian was also the son of two Dragon Kings, someone who had fallen from god level, so he could not be included in any normal comparison.
When the Snow Empress had failed to condense dual soul cores, even her origin had suffered grievous damage. Her chances of surviving her next heavenly tribulation had dwindled to almost zero, forcing her to possess a hundred thousand year snow lotus and transform into human form to cultivate anew.
The Snow Empress had certainly made a clown of herself in the original story, but she still possessed considerable strength. If even she had failed to achieve yin-yang complementary twin soul cores, one could imagine how difficult it was.
Both sets of experience Long Xiaoyao had given Jiang Yue concerned Isotopic Resonance. Even if the Evil Eye Tyrant had been unwilling to fight Ye Xishui