It used to be that you could not IPO unless you were profitable, and furthermore the point of an IPO was to raise money needed to fund growth. But today these companies have raised enough money from VC's that they don't need any more from the public markets. By listing shares and letting these insiders sell, there is more limited supply and great demand, so they can sell tiny stakes for inflated prices. It's really great for VC's and other insiders.

I don't think it matters. I think the main difference is an IPO is typically used to raise money to grow, where as a DPO is mainly used to shift risk from VC to the main street and allow VC to recoup money from a non profitable entity. A magic trick really. IPO's do that too, but with a DPO there isn't the expense and the risk dog and pony show. Similar but different.