It's not just that the reward for joining early is smaller than it used to be. It's also smaller compared to joining later. The marginal utility of money is actually what's causing the problem. If I can join a company late with very little risk and a much higher chance to make a few million, I'm probably much less incentivized to join a company early with the risks associated with that.

But in this system the incentive to join early is still several multiples, mind boggling multiples, of what it is to join later.

Just as the risk is much, much higher. People just hear about those few who became bi/millionaires out of IPOs, not the thousands that never made it.

And how much would that be? $100M? Which would generate a few M USD per year of disposable income?