- Buying allies. If you make a lot of other people rich, they will probably become your biggest boosters. Might not be a bad idea to have some rich allies rooting for you. And you might need some political favors in the future.
Using a dual class stock structure, you could even retain complete control of your own company while gaining partial or complete control of others with the proceeds of the IPO. My understanding is that private companies usually don't have dual class share structures until they are preparing to IPO. By IPOing in this manner, you are giving patronage to the investing public without ceding control of the company's assets and operations, in exchange for a boatload of cash right now.