Because 95% of businesses are started by people who don't know how to run a business.

Most people who start companies are subject matter experts. They're people who are really good at what they do, and have a wealth of knowledge in their field. Often times, the company they work for couldn't function without them, and they see what the guy on top is making and think to themselves “Why does he make the big bucks when I'm the one doing all of the work?”

But the thing is, subject matter expertise is just one piece of the puzzle. You can be the best Chef in the world, but that doesn't mean you’ll be good at managing a restaurant’s cash flow or staff. You can be an awesome programmer, but that doesn't mean you'll be able to manage a team, scale beyond your own abilities, find clients, and close the sale. You can be a hell of a carpenter or general contractor, but that doesn't mean you'll be good at pitching to customers, consistently finding work, and balancing your books.

Ninety five percent of businesses fail because they're started by people who only understand the core of what the business does - not how a business runs. They don't know leadership. If you don't have experience managing people, managing cash flow, how to market, or how to manage everything else that falls outside of your work-knowledge, you will crash.

Source: quora dot com

True