As I understand trading exchanges are done as a pool. If more people come in with fiat to buy ETH and they take out ETH to put into the ICOs then they have a problem in that they may not have sufficient ETH when mass withdrawal occur. They will not be able to change your fiat or other cryptos to ETH thus resulting in delays to your exchange. It is probably why they are quite about the situation because a possible run on their exchange might ensue.

A lack of liquidity does not just mean liquidity in fiat terms but also in cryptos terms. Exchanges only have a limited number of the different cryptos they trade. It is just the same way the banking system operates because they assume that a certain proportion of the trader will kept their cryptos on the exchange.

This is also why many tell you not to keep you cryptos on the exchange and to keep them in your own personal wallet. Coins on the exchanges do not belong to you unless they are taken out of he exchanges.