I owned stock in a company that will, very likely, never go public or get acquired. It doesn't need to. Because of the shareholder agreements, I could only really sell back to the company. Sometimes they were amenable to buying, other times they weren't. Essentially, I was playing in a monopoly market, except the monopoly was on the buyers side. Fortunately for me, the majority owners were much more generous than they needed to be. Without that, I wouldn't have been able to make anything from the stock.
There are numerous tax pitfalls along the way were you can get absolutely ruined if you do it wrong. Exercising options can very easily become a non-trivial investment in actual cash.
None of these details are particularly predictable when you start out.
Ownership is ownership, but details matter. There is a long way between signing an options agreement and true ownership, liquid or otherwise. The longer that path, the less certain the payoff, and the less valuable the options.