Well, I accept the term boss doesn't fit well. But still, in very competitive institutions you need to deal with lots of politics, do post-docs over post-docs to get a lab of your own or at least be more in control of the research. I think a startup that is financially successful is a good shortcut to that. You can become a CTO and go whatever direction you want.
Of course it's hard to build a team as a PhD, at best you can get some reasonably competent master students to do some work for you.