IEO is being popular now because of SCAM ICOs before!
People especially investors are afraid of some ICO and this cause failures to reach softcap before.
Now IEO is here and the shine of PUBLIC sale is coming back again!
IEO by itself does not guarantee anything to investors. Only by participating in the IEO on top exchanges with an impeccable reputation, investors have at least some protection against fraud. But in all other cases, the risk for investors is not much less comparing to traditional ICO. There were already enough cases when new exchanges were hosting IEO, and after a while their website stopped working