I think that the ICO is no longer profitable for both the creators of the project and investors. ICO now can be compared with children who play in the sandbox. IEO make a profit ! Sale through the exchange gives confidence that the project will be traded on the platform where the IEO is conducted !
ICO no longer viable as a way for crowdfunding, IEO has really taken over the market and investors like it as they will see right away in an exchange after the sale is over. I don't know how the contract looks like between the team and the exchange but as there is an assurance it will be listed right after, that is very attractive to investors.