In my opinion, IEO is not for crypto startups that are seeking funds to kick start their project but for projects that have raised capital already or have rich advisor and team to fund the project. Fund-raising through IEO can be very challenging for startups that need money to kickstart their project, because they will need large amount of money to conduct their tokensale on good exchanges, as this exchanges only list projects that meet their legal requirements and can also afford to pay their listing fees. So the best means to raise money or capital for new projects is to present their proposal to Venture capital firms or Angel investors.
Well, doesn't the project that conducts the IEO also offer proposals to angel investors? it's just that their system is different, they use a third party just consider him a broker.
Why does the IEO exist? because IEO is a new innovation from ICO that has been filled with scammers. So the IEO exists to secure investors' money, but still in the goal of finding investors to develop startups.