Companies with limited name recognition outside of their industry--Okta comes to mind--may not be able to scare up enough liquidity in the marketplace to absorb the millions of shares on offer by the company. A true unrestricted dutch auction may end up going off close to zero. That's what the IPO roadshow is about, giving your pitch and soliciting bids for shares. The investment banks act as gatekeepers to these potential investors, and arguably getting face time with their clients is a large part of what the fees the company pays are for.