Because your acquaintance has knowledge, skills and abilities that allow him to utilize tools like a press or lathe to mill whatever he wants. In that case I trust he is also thoughtful and disciplined enough based on those exhibited KSAs.

Not so with the fab machines of the near future. Any fifth grader who can plug in a fab machine and download a template could do what your acquaintance can, without the years of experience and maturity to ask the question "should I do this?"