We know that ICO was once popular, and reached its heyday in 2017. ICO's popularity declined when fraudsters used ICO to commit fraud, make fake projects, and then run off investors' money. Investor confidence is declining, it has a bad impact on the ICO project. Until the trend changes and IEO becomes the best choice because it can increase investor confidence, especially what is done in a trusted exchange.

IMHO, ICO can be popular again if public fundraising efforts are supported by TOP exchange. This was done in 2018. But it looks like IEO's popularity is still unbeatable.
https://t.me/ico_analytic/600