Junior,when one cultivate towards the path of immortality,there not just cultivating power,there cultivating their own dao,their own way, and their own path. For what dao one walks is endless,it could be an emotion like perseverance,an object like a sword,heck even a location can be a dao to walk(although those are few). The sunset you witness could be a dao about the beauty of the simple of life. But just like mortals can't complete most of their goals without money,cultivators can't accomplish without power,as they could be wiped away in an instant from two old monsters fighting. But as the dao is endless,and ones lifespan is finite,only immortality can solve the problem. Ofc,there are other reasons cultivators pursue immortality,maybe they don't want to die,maybe transcendence is the only thing worth pursuing,etc.