It really depends of the stage of the startup. I recall reading someone doing analysis on this (unfortunately I don't have a link) showing that joining a company that isnt public yet, but is already large-ish and showing some real product-market fit gets people better payouts. Yes, employees 1-40 of a future unicorn will to great (if they could afford to buy the shares, and AMT doesn't kill them which is another story), but it's relatively safe to get into a company that hasn't IPO'd yet.

Imagine say, that you joined Stripe in 2014. By then, probably 500-1000 employees and a a real name on the industry, yet private. It's perfectly reasonable to not consider the stock they might have offered at that time as straight out money, like you'd have treated Google RSUs. But discounting the shares to zero, or just "a nice bonus" is also silly. I bet anyone that got a year or two of stock in that era is well into the retire-early/somewhat rich cadre, and that wasn't all much of a risk.