Why All for One didnt keep a regeneration quirk for himself?

Question

According to Super Regeneration - Boku No Hero Academia Wikia

This Quirk has the ability to regenerate any sort of injuries on the user's body, such as missing limbs, at incredible speeds.

All For One once stole and tried to use this Quirk to heal himself from the heavy damage All Might caused to him, but because his body had already cicatrized those injuries, the Quirk had no effect and was considered useless.

So, because he couldnt heal the injuries he already cicatrized, he considered this quirk was useless. That doesnt seem to have any sense. Why he didnt keep the quirk to heal new injuries in new battles? That would seem to be a very useful quirk, even if fighting All Might again.

Answer 1

When All for One first appears in the manga in chapter 59, he talks about, how he wished to have gotten the regeneration quirk sooner (it probably took a long time to get that quirk, since it is so rare), because his wounds had already healed at the time, when he finally got his hands on it. So for those injuries, which had been caused by All Might, the quirk was useless.

But it doesn't say anywhere in the manga, that he doesn't still have it. So, it is very likely, that he still has it and uses it for new injuries.

Answer 2

I see it like this is you cut off your arm just below the elbow and use fire to cicatrized the wound then the regeneration quirk would not right. But if you then cut your arm again after cicatrizing the stump at the shoulder would regen regrow the whole or to the stump