Lu Yu wanted to obtain the Earth Spirit Bead, not because he thought it was valuable and wished to possess it.
But because of the Earth Escape Secret Technique.
He hadn't cultivated earth elemental power, and even after learning the Earth Escape Secret Technique, he couldn't use it. Using earthly treasures to perform earth escape required a long casting time, which wasn't very practical.
However, owning the Earth Spirit Bead made it possible to perform earth escape with external objects, significantly reducing casting time.
If the spiritual qi in ordinary earthly treasures is like a motley militia, the spiritual qi within the Spirit Bead is a regular army, and not just any regular army but an elite unit, which is not only easier to command but also countless times stronger in quality than a motley militia.
