Because, starting a company, and running it for a long time requires very different set of skills and mindset. And it's a very different experience, and people

Because, starting a company, and running it for a long time requires very different set of skills and mindset. And it's a very different experience, and people are different. Also, the most successful entrepreneurs actually continue to create companies, often in very different areas: Elon Musk, Richard Branson, Martin Varsavsky, Oleg Tinkov.