Also, what if you can't sell? Selling is at their discretion. They can prevent you from selling some of your so-called "equity" to keep you on their leash as long as they want.
But it's a private venture and not a public company, and you "can't sell" that holding on a market, only via complicated schemes that have to be authorized by the board. But you'd take it anyway in the expectation that it would be liquid someday. The employees are in the same position.