Corporate jobs often don't offer those things. You usually build what others tell you to build, follow orders and have little voice in your own future.
Can you imagine if the team at 37 Signals had corporate jobs? They wouldn't be rock stars, they'd be cube-dwellers with no blog, no chance to make big changes, with vague titles like "Lead Web Designer" or "Enterprise Architect." David Heinemeier Hansson wouldn't be known as the designer of RoR, he'd be that kid who came up with the non-corporate-standard framework that got mothballed after he was laid off. The people left would complain when they got assigned to port his weird "Ruby" apps over to Struts.
Entrepreneurs, from the person who opens a McDonald's franchise to an Ivy Leaguer seeking millions in VC want more or less the same thing, and for them an "exit" is often just icing on the cake.
I'm not trying to argue that entrepreneurship isn't a great path to pursue for many people, but I disagree with the simplistic picture that people sometime paint wherein entrepreneurship is always glamorous and employment is always dreary.
Disclaimer: I work for Facebook.
It doesn't always always have to be about money. Open source software gives people to build something, break some new ground and make a change. I guess that's the same drive that gets people to found or be part of all kinds of efforts that extend beyond software and startups.
It's no coincidence that founders who get bought by BigCo's end up looking miserable 12 months down the line, after being demoted to an employee, who doesn't have full control of their baby any more.
"Can you imagine if the team at 37 Signals did corporate consulting? They wouldn't be rock stars, they'd be design whores with no blog..."
Lots of people who have "real jobs" also have outsized online presences, have gone on to fame and relative fortune because of their off-hours OSS contributions.
Adding VC to the people who don't, sure isn't going to change their path.
I agree with your definition of entrepreneurship - a chance to lead, to do it your way, to have a voice in your own destiny.
Which is why I'd never, ever, ever take funding, and risk having to manage the expectations of someone whose goal wasn't a fabulous business, but the biggest/fastest exit possible.