There are so many examples to the contrary of this that it'd be exhausting to list them all. IBM had lived many lives of men and was long past being a startup when it helped create the PC industry; seriously, that company was pivoting before "pivoting" was even a term in usage. Apple was a long-toothed public company when it reinvented portable music and, later, smartphones. We're still observing the fallout from the iPad, but it's safe to say that was a game-changer in tablet computing, too.
I'm not saying that to kiss these companies' asses, either; these products genuinely redefined the marketplace. And both companies were public and had a checkered history already when they reshaped these markets. I remember cellular phones before the introduction of the iPhone. So do you.
Saying that the only innovation happens over lattes in SoMa is just so blatantly wrong that I wish I could persuade you otherwise for your own well-being. (Before I forget, thank you for the compliment regarding my comment; though I still disagree with you, I do appreciate the nod.)