Lots of organized crime around the world manages to operate without cutting all the limbs off somebody then arranging them like flowers in a "vase" made out of the poor soul's ribcage. The cartels take violence far beyond what is pragmatically necessary. Their system of crime breeds excessive violence and insanity.
This stuff mostly followed after the zetas. It was a very deliberate strategy to compete in a hostile landscape that others eventually copied to survive.
It's notable that a lot of the Zetas came from a military special forces background, making it seem as if their extreme brutality was a strategic choice inculcated during their training.