Personality traits play a huge role is starting business. And those are modifiable only to a certain degree. I have a very modest business of which I am the sole employee. I could, of course, try to hustle, hire employees, expand etc. But, I actively dislike, am disinterested in, and am not suited by skill set for that.
I'm very introverted, as are many on this board. Being introverted is NOT a bug, it's a feature, but it does provide an inborn barrier to business development in many areas. Some of the introverts here have in-demand skills, but some do not. Personally, it would make me anxiety ridden and miserable to have to hustle for clients (I typically avoid using the phone, and I don't like to talk to people that much). So I would have to partner with someone who could do that for me...but that comes with the hassles of partnership. I have served as a supervisor in past jobs, and I find having employees extremely tiresome and draining. So then it's back to business that I could do solo, or with a trusted partner.
Basically, in order to be content and do productive work that I'm well suited to, I need to be left alone, to set my own schedule (not jumping to meet potential clients' schedules at short notice); I prefer to be far from civilization and cities, by myself, collecting biological field data; reading; working with plants or wildlife, etc. I'm sure there are opportunities to make big bucks within my skill-set (I'm still waiting for a lightning strike Big Idea), but not as many as if I was naturally inclined toward marketing, finance, computer engineering, specialized law, or generally more social-oriented work, etc. I have arranged my life to maximize my talents to some degree, but at a trade-off of higher income. I could do more contract work to boost income, but I have obligations at home so I can't travel constantly or for very long periods.
I'm not whining about this...I don't feel the world owes me an opportunity to maximize my personal snow-flake self and ALSO reward me with tons of cash. And OF COURSE if making money was my primary motive in life, I would suck it up and suffer through the things I hate to make it happen. My father did this...built his own real estate business, retired early...classic millionaire next door. He HATED his work (though he was proud of his accomplishments) and constantly said wish he'd done something else. Yes, he had money and security, but he was mostly an overworked, pissed off, and unhappy person. It's not worth it to me to go that route, unless I naturally enjoyed the work.
I really think those people who have personality traits more suited to business ventures severely underestimate how hard it is to change your basic talents and inclinations, to find and optimize opportunities, and to identify the more specialized niches suited to less outgoing personalities.