Prominent artists having an array of assistants and understudies who do most of the detailing, while they themselves focus on more important matters like choice

Prominent artists having an array of assistants and understudies who do most of the detailing, while they themselves focus on more important matters like choice of subject, medium, technique and composition seems to have been the practice in the times of the Florentine and Roman masters, as I read from "Agony and Ecstacy". Even architects do something similar, did Zada Hadid design every cornice and every pillar? I guess its the same with law firms also.