I've worked two startups and two public companies (and a University) in my career. Other than the small salary, I made nothing from the startups. The first public company made me enough to buy a house in the Bay Area and the second made me enough to fund my own startup as well as invest in others.

So yeah, my experience tracks with yours -- all my wealth was made working for public companies (that I happen to catch during their biggest periods of growth). To be fair though, that may change if my investments work out. Then most of my wealth will be from investing in startups.