This is true, but you need to look at who they actually are. The majority of folks who become fabulously wealthy off of equity (read: owning a piece of a business) are the folks who start those businesses and manage to hold on to most or all of the equity.

Most of these businesses are obviously not in tech, but if you want to filter out non-tech companies, the power law distribution of equity-derived wealth in Silicon Valley still doesn't favor employees, even those who join companies early on.

It's basically like being paid in lottery tickets. Fine so long as the rest of your salary is enough to pay the bills, not fine if you depend on it for your retirement, and either way, some of us would prefer the well defined payout of cash.

It may seem hopeless, and indeed many other factors do make good product companies fail. But when other factors do NOT intervene, then the remaining value does depend on your execution.