system
Given the following post, respond as if you're commenting on Reddit:
human
[Dragon Ball Z] The Dragon Balls become inert if Kami/Elder Guru dies—so why would they not just wish on the Balls themselves for immortality, to prevent this? Seems like that would be pretty easy, especially given how long-lived Namekians already seem to be.

Same question for the whole “if the Supreme Kai is killed then the God of Destruction is killed as well” thing—why then wouldn’t a Supreme Kai take it upon themselves to wish for immortality to avoid such an eventuality, especially in the wake of foes like Bibidi/Buu or Moro, as it would mean the whole universe falling out of wack if this were to happen?

I mean, hell, why doesn’t *anybody* wish on them for immortality?? The only ones I can think of who even tried that plan were Frieza (actively prevented by the Z Fighters), Future Zamasu (who did it, was successful, and *they had to get Future Zeno to destroy the universe* to stop him), and *Emperor Pilaf* (joke character), and *maybe* Vegeta (and Nappa)—but only in the interest of beating Frieza, who also had that plan. 

EDIT: Did more research and apparently more characters succeeded at this than I remembered—Garlic Jr. and Lord Slug both succeeded at wishing for immortality, and King Piccolo succeeded at wishing for eternal youth, which isn’t exactly the same.
gpt
In the case of characters like Goku and Vegeta I'd imagine they would not want immortality cause it would remove all the stakes of becoming a better, stronger fighter. Their whole life is pointed towards becoming stronger through training and fighting stronger opponents becoming immortal would be considered cheating or at least boring by them.
Also if you can just teleport from the afterlife back to earth you are kinda immortal.