>They'll likely get a better valuation from the public market than they would privately and the founders who have been waiting 10 years can take some money off of the table.
This is really all there is to it. You don't actually have to build a business anymore to get rich. You just put together something that looks like one, pay yourself a handsome salary for 10 years, then cash out and retire to New Zealand.
Sweet gig if you can get it.