It's not completely dead yet now since there are still some upcoming projects. The reason why IEO come is that most investors don't trust it anymore because when it enters in exchange there's really a big difference.
yes, it gives a guarantee of being registered in the market for IEO tokens, but it does not guarantee that the project can survive on the market. or guarantee the price will be good. because the development carried out still depends on the team that works hard for their products. so keep doing your research before you invest in ICO or IEO.
Not only that, it doesn't even guarantee that the project is even legitimate at all, never mind about the survival. Looking at only the past two IEOs I know of, they died within a week of listing, and their channels died even faster, except for all the angry investors of course (but what were they expecting, people would buy useless tokens from them at 3x on listing day?).
Stay away from IEOs unless you actually love the project.