This is harsh, but true. I've never heard a successful founder say "I don't know, I just wanted to start a company with my friends and get rich." Every dang middle-schooler in the US wants that. Companies are a means, not an end. Successful ones always start with someone who's passionate about a very specific problem.

This really comes out in corporate mission statements. Even if you're Xerox, your mission statement is something like "Improve the rate of business communications by creating the world's most excellent copy machines."

If you don't have an idea for a startup, you're missing the key ingredient. The team literally cannot exist without that visionary person who knows exactly what they're after.