Some companies that conduct IEO cannot reach 100% of the sale of their tokens, everything of course depends from the exchange itself, how popular it is and of course much depends from the company itself, not all investors will want to buy tokens of a company whose ideas and plans are unrealizable.
basically ICO and IEO can be used as a place for scammers. but, we know that by seeking information first, it can be avoided. however, currently the IEO is still better than ICO for several reasons. although there are some opinions that people can be cheated from the IEO.