I really think these IEO thing is only good for the top exchanges and these is because they have the liquidity and the traders to pump a coin after listing, which is why their IEO projects are usually successful.
But the smaller exchange don't have the same and their IEO success rate is no way near the top exchanges. Maybe 2 out of 10 IEOs conducted on the small exchanges would succeed, while top exchanges boast of a success rate of like 9 out of 10.
I agree with you, most of the IEO held in global exchange like binance and bittrex tend to be highly successful and some of them sold out in less than two minutes, but the IEO conducted on small exchanges takes very long time without the team meeting their soft cap, some project even complain of not making any sales.