maybe that's the main reason because binance is one of the biggest exchanges in the world, of course people will buy IEO coins held at binance.
however, IEO does not always run smoothly. In some other exchanges there are losses, but it doesn't seem to affect the IEO in binance.
The consequences are directly linked to the reasons that weaken the profitability of the IEOs on other exchanges. The Binance IEOs are an exception because the limits and conditions for IEO participants are different, easy for loyal customers. Just holding a lot of BNB can give a special advantage in both token sale and trading the altcoin pairs.