But vesting stock options are already a scam to keep you there and gamble about whether they will have to pay you. They also minimise things like payroll tax they the company pays.
They're handed out like candy instead of pay rises and performance bonuses. Half the time you wear the tax liability on today's price at grant time (and consequently your real take home pay is lower as a result). The fake income is counted toward lots of things like tax concessions, government benefits, etc, which means your out of pocket expenses can rise based on income you never earned this year.
If they dont increase in value you never make up that loss. If they increase in value then you wear capital gains tax on top of the income+benefits tax you already paid. At the end of the day, your take home pay for a bundle of stock options could easily be half or less what the equivalent cash amount would have netted you.
And adding insult to injury, if you quit or are laid off you lose the un-vested options but can't claim back the tax you got fucked out of.
Tl;dr: vesting stock options are a rort which only benefits the company. The employee doesn't usually see any real benefit from them unless the company is continuously wildly successful.