Because Exchange taking some comission about 10 to 20 % from total fund raising.
If any IEO is making loss of investor(trader of exchange), its same like ICO loss...
Exchange and project both are equally responsible...
Yes investors are more comfortable investing in IEO than ICO's that is why you see majority of former ico project are opting for IEO, nobody is willing to invest in a project that will end up to e scam and team will run away with funds, i myself will rather go for an IEO project than put money on ICO, too risky it seems, exchange will definitely take their percentage after all once IEO has ended trading automatically begins, no more listing stress.