If you are only looking create value __only__ for early investors, then extracting all there is at IPO makes sense. But if you are looking to create value for employees who have given their blood, sweat and tears, it would be helpful to leave some money on the table to generate more demand and signal market confidence.

In the case of $UBER, from reading the axios piece, they seems to have extracted all there is from private market and the demand from public market appears to be even lesser.