One benefit is that stock is typically awarded in the form of a multi-year grant, where the number of shares is priced at the time the grant starts. So if the original grant says you get $X worth of stock per year for the next 4 years, and then the stock price goes up 40% in Year 1, you’re now effectively getting $1.4X worth of stock per year for the remaining 3 years.
To illustrate this, imagine at offer time, you're given $150k + $80k worth of stock over 4 years. That works out to $170k per year. Nice, but not even doctor money. The stock is currently $100/share, so that's 800 shares. Now imagine the stock 4xes (not unusual in tech). By year 4, you're making $230k, without having had to beg for a raise or anything. This is how people end up with ludicrous total comp in tech.
