The opportunity cost of this restriction on their lives is huge.
Had they gone public two years ago, employees would have benefitted from a market of a lifetime, with equity in one of the best tickets in town.
A lot of life changing early retirements and "Fat FIRE".
What restriction, exactly?
Or to phrase parent's point differently: by not IPO'ing, Stripe forfeited the premium public markets would have been willing to pay Stripe employees for their stock.
Let's say they went public in '21 instead of raising money in June of that year. The market would've already turned by the end of the lockup period. By delaying the IPO there is still some chance that the shares can be sold on the public market for more than the grant price -- I would note that this really benefits Stripe hired post-2020 but at this point that's like 75% of the company.