Because they (should) have sophisticated risk models that account for the long tail. If even a few ipos become Google or Facebook, the risk is worth it. But for average retail investors ipo participation will be bag holding exercise. That said betting your conviction is one of the only ways to beat the market, even if it comes with additional risk (emotional+intellectual attachments). If you really believe in ai or space exploration, the upcoming ipos represent an opportunity to bet on your beliefs and predictive capability