I think soon the popularity of the ieo will end and the old ico will begin. There is more transparency and less manipulation.
If you study in detail, you will come to know that IEO is kind of updated form of ICO and has actually offered great features to cover the problem that have been wide and large in the time of ICO. You get to invest in a good project is enough good IEO is doing the investors because the digital exchange always make sure they evaluate the project before conducting IEOs and listing the tokens.