There is value beyond IPO- companies continue to sell ("issue") shares on the public market as a way of generating cash. They also buy back shares when with excess cash, usually when the market value is low but sometimes, irrationally IMO, when it is high. They also use this as an incentive-backed compensation pool. The relative value of these is debatable, but I don't think it is correct that post-IPO public shares are just traded between third-parties making short-term bets. Happy to be corrected.