It should be known that before Pei Xuanjing, whether it was his original Daming World or the world he was projected into, a cultivator's ascension in power also meant the evolution of their life, granting them a much longer lifespan.
Cultivators defied the heavens and endured immense hardships in their cultivation. Aside from their quest for immense power, their fundamental goal was to gain an even longer lifespan, allowing them to exist undyingly in the world. This is the true aim of practicing cultivation.
All actions are aimed at realizing this goal. If one cannot achieve longevity, what could be the significance of having great power, if not for engaging in destruction and battles?
Take the Daming World for example, where the continuous increase in one's strength also led to a continual increase in lifespan.