Just because stock options should be valued at less than a company's private valuation does not mean they are worth 0. Very few engineers actually value them at zero.
Adding on to this comment:
It's a spectrum, not a black and white your options are worth zero dictum. At one end, (extremely early stage startup, < 5 employees, you're not a founder) your options are probably worthless, sure, although you have a minuscule chance of being worth $10M+. At the other extreme, you join a company that everyone knows is going to go IPO within two years, and essentially earn what you would earn at Google or Facebook, maybe slightly more.
To give you one example, I knew someone that made about a million (vested over 4 years) in options by joining an already-successful startup as engineer ~70, that he believed would IPO within 4 years. On top of his market rate salary.