What I read once: when you're a wild animal in the wilderness, just scarring over the wound sometimes gets you back in action faster than regrowing the limb, and that's a survival advantage.

If that's the main reason evolution usually went this direction, then maybe there's not much downside for modern folks.

No? Fun fact: young children who have finger tips cut off sometimes can regrow them

https://www.npr.org/sections/health-shots/2013/06/10/1903854...

If the cut is clean, i.e. amputated by a scientist or vet there are no drawbacks to the regenerated limbs, but if they get into fights with other axolotls and the limbs are "half-off" they sometimes regrow deformed.