Why couldn't Shenron make Android 17 and 18 human?

[MasenkoHA]

That always bugged me. He can bring the dead back to life, grant immortality, and restore youth but reversing man-made modifications on humans wasn't within his power? Really? Of course the meta-reason was without her cybernetics Android 18 would have just been a normal woman like Bulma and wouldn't have her fighting abilities and super strength and maybe Toriyama wanted at least one tough female character or maybe he liked the irony that a guy who was far weaker than Goku and Vegeta got the strongest wife. But in-universe it doesn't make much sense to me

[Doctor.]

Same reason he couldn't kill Vegeta/Nappa and why Porunga couldn't teleport Goku. He can't directly affect beings with stronger power than his creator, and 'indirect' actions require consent. Granting immortality is just bestowing a gift on to someone; wishing someone back from the dead doesn't need consent because, well, they're dead (and they don't have much power when they're dead, too). I guess the only outlier here is restoring youth. You can't really excuse it by saying one was made by Kami and another by Dende, considering Dende's dragon has been portrayed to be much more powerful. But Shenron's limits have always been very arbitrary - they have to be, for the sake of the story.

[Kamiccolo9]

Same reason he couldn't kill Vegeta/Nappa and why Porunga couldn't teleport Goku. He can't directly affect beings with stronger power than his creator, and 'indirect' actions require consent. Granting immortality is just bestowing a gift on to someone; wishing someone back from the dead doesn't need consent because, well, they're dead (and they don't have much power when they're dead, too). I guess the only outlier here is restoring youth. You can't really excuse it by saying one was made by Kami and another by Dende, considering Dende's dragon has been portrayed to be much more powerful. But Shenron's limits have always been very arbitrary - they have to be, for the sake of the story.

The whole consent thing is a bit...odd.

Porunga couldn't bring Goku to Earth against his will, but he was able to bring everyone on Namek, including Vegeta, to Earth without, as far as we know, asking everybody's permission. I don't remember everyone's reaction, exactly, but I do recall all the guys on Earth being surprised, and Vegeta, Gohan, Krillin, etc., were all indisputably stronger than the Eldest Namek.

Honestly, it feels like the whole "certain wishes require consent" thing was just a last-minute asspull by Toriyama to have a happy ending to the Freeza Arc, while also keeping Goku off Earth long enough for the plot to happen, which certainly matches up with how Toriyama handled Goku during the rest of the arc.

Leaving out the Androids and their bombs, as that's a Dende's Shenron thing, and I guess you can say that the rules are different or something. But Porunga's issues are pretty blatant when you look at the wishes for more than a few seconds. His limitations on mass revival are clearly only there for plot, as you'd think that the Eldest Namek, having created the Dragon Balls, would have made them capable of reviving the whole race, rather than having to spawn a whole species of new Namekians by himself. But it makes for better drama, and, to be fair, Kaio's strategy with the wishes is pretty nice.

[Bulma's Foot Masseur]

I think not requiring consent depends on how easily-reversible the wish is. After being wished to a different location, you can go back. After being wished back from the dead, you can die again. Reverting to non-human status without Shenron's help, though? That's way further along the spectrum than removing a bomb, which Bulma could probably re-insert just as quickly.

[blain218]

Because they already are human. Dr. Gero only enhanced them on a cellular level according to Toriyama. Plus, Shenron can't alter the nature of anyone stronger than its guardian according to what is stated in the series.

[Doctor.]

Oh yea, I forgot Daimao is weaker than Kami, so Shenron's restrictions work.

[Banana]

I think not requiring consent depends on how easily-reversible the wish is. After being wished to a different location, you can go back. After being wished back from the dead, you can die again. Reverting to non-human status without Shenron's help, though? That's way further along the spectrum than removing a bomb, which Bulma could probably re-insert just as quickly.

Are spirits capable of providing consent though? I know this is about to get dark, however I'm sure some people for instance in the millions that were killed by Cell may not have wanted to have been wished back. I'm also curious as if they would remember what happened. I know not quite the same thing, however Krillin and Piccolo remembers the moments just as they were being turned to stone by Dabura's saliva. I guess that might be a little different though because they weren't technically dead there, just not really existing lol.

[kn83]

Because 17 and 18 are already humans.