How many people come from companies with large exits like that? We're talking what a total of 200, 300 people tops? It seems pretty unrealistic to expect most "top talent" to be in the situation you describe.
You also don't need a big exit - every single big name out there keeps issuing stock and it keeps vesting in someone's account. E.g., considering the stock growth I'd be surprised if any AAPL or NFLX engineer who spent 5+ years with the company is not a millionaire.