Another point to consider is that one person can do all of the jobs required to get the parts made.
Not all people, when a person is made to wear many hats, (take on many different responsibility's) things suffer usually quality and efficiency.
Some people can over come this, more people can't or are not willing.
"Let me tell you the secret that has led me to my goal: my strength lies solely in my tenacity." -- Louis Pasteur