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.