This is true. Famous exchanges like LAtoken went being a scam just because of bad IEOs.
Binance is much trusted and people hold BNB tokens in the exchange mostly because they want to be the first to buy the IEO token and investors blindly put their money on any IEO because they know they would get a profit. If binance started adopting any IEO, not only people would not trust the platform, it's BNB holding strategy would also backfire making it's token valueless.
When it comes to Latoken or P2PB2B, I think these are two shit exchanges in the crypto market because all the coins here have no liquidity and of course nobody dares to invest in IEO here because of the great risk. In fact, there are only a few exchanges that can perform well IEO like Binance or Huobi because these are the only two exchanges that help me make a lot of profit in this market and not have to worry about losing money when participating.