Successful businesses in these construction fields were started a generation or more ago and handed down to family members.

Even electricians and the like have a very difficult time getting beyond self-employed with an assistant and maybe a partner who helps part-time with billing and scheduling. That leap to getting a second employee who can work independently in the field is a big one. Why is that person working for you rather than themselves? A good portion of the time, the answer to that question is that they are related to the owner in some way.