While an IEO is come, it definitely be trade in exchange irrespective of the price volatility. But, if you have participated for the ICO then it is not the time burden when it will be listed in the exchanges. I know there are many ICOs which were came in the year of 2017 but still now many of the crypto haven't listed in any exchanges. But, IEO directly lunch on a exchange platform. So, it is good some how.
For investors, the most important thing is to quickly list in the market and the IEO can make a project be traded faster. For developer teams, ICO requires negotiations with exchangers for listings, unlike the IEO because in my opinion this includes packages offered by exchangers to the developer team