Having just done a half-assed plastering job, I will answer that with "because a lot trades needs practiced skills, not just the knowledge". Sure, it'll be one

Having just done a half-assed plastering job, I will answer that with "because a lot trades needs practiced skills, not just the knowledge". Sure, it'll be one more thing that eats into bits and pieces of what we need trained labour for, but it won't eliminate it.