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human
[Dragon Ball] Why didn't Vegeta or Gohan's tails grow back?

At the end of the Saiyan Saga, both Vegeta and Gohan get their tails severed. Goku repeatedly grew back his own tail until Kami "pulled it out from the root" (whatever that means) and Vegeta claims that his tail will just grow back to the doctor when he first returns to the Frieza Force. So why exactly didn't his tail grow back? Even if the claim is that Vegeta was already an adult and so it would never grow back for some reason, why didn't *Gohan's* tail grow back either despite Goku repeatedly losing his tail in childhood?
gpt
It's been revealed that after a certain point Saiyajin bodies view the tail as a weakness and do not regrow it as the Saiyajins reach a certain strength seemingly in preparation for Super Saiyajin. 

This could be seemingly supported by the fact that Goten and Trunks were born without tails, and they had incredibly high battle power and achieved SSJ with ease.