IEOs boost the trust level of investors, this alone makes a big difference.
You are right, but investors must be more careful of what he is believing. By the increasing number of IEO and its hype, there will be more scammers to take this opportunity to scam investors. Also, IEO is just ensure listing and not ensure that the project will be developed well.
IEO becomes risky for those who would still not use their mind to invest in projects confirmed by top exchanges like Binance, because it is obvious that smaller exchanges are after money and not integrity, if a scammer offers them huge amount of money to register their project, they will gladly accept it and give a sorry excuse later for registering a fake project.
IEO for now should still be safest and most secured means of investment for investors, but then we need to be careful of the exchange we use and also still do our own research on those projects to be sure they meet up to the required standard that is necessary for the project to become successful.