In my opinion, a "successful investor" should also have the vision to include someone with a passion for the business and not use someone's excitement to extort a free internship.
I'm not sure I understand your post. It sounds like you think investors are somehow cheating "interns."
From the employer's prospective, interns are not free. Rather they COST a lot of money. It takes twice as long for me to do anything while I'm training someone to do it, and expensive mistakes are often made regardless of how comprehensive training has been. (We have all made expensive mistakes in our own investment careers, so I'm sure everyone knows what I mean.)
Then, when the intern is finally at the point where he is truly contributing to the business, he realizes he knows enough to venture out on his own and the employer is left to train another staff member.
This is time-consuming, tiresome, and costly.
Twice I tried hiring people interested in real estate, thinking the person would evolve from an assistant to a business manager. In both cases, they left as soon as they felt able to take on the world of investing.
My next assistant will be an empty-nester stay-at-home parent or a retiree who wants to be useful and make some extra money. Either way, it will be someone with no investing aspirations of her own.