The art of the Soul Pill, although greatly beneficial for Core Formation, is not an easy feat to achieve; in fact, it could be said that it's as difficult as the Core Formation itself.
Condensing a Soul Pill requires an immense amount of Soul Power. In other words, only Soul Cultivators can attempt to master this secret technique. In the entire Cultivation World, Soul Cultivators are few and far between, and in many areas, their existence is even considered taboo.
Even for Soul Cultivators, success is not guaranteed.
According to the Jade Scroll, Xi Cangqiong succeeded in cultivating the Heart Cleansing Technique to a very high level and then used the Soul Suppressing Kettle to refine a significant amount of Soul Power, which led to his fortunate success.
