I would not say that IEO sale guarantees that the user will easily and quickly invest. Care is always needed because the projects themselves are not always ready to provide good service, saying we are IEO token. I am watching a project that has been delaying sales for several months. Good startup are able to find investors in any case.
Users are naive. I also participated in many ICO projects, and even some teams were so convincing that I was ready to invest. But over and over again I saw how, after the pre-sale, the tokens became empty. The most important rule that must be agreed by people willing to invest in ICO, IEO or STO project is be patient. It is good when the startup has private sales before IEO sale on the exchange. It demonstrates the ability to attract investors and fulfill their obligations.